feat(translation-ui): tighten settings/onboarding UX around the translation feature

UI refinements on top of the translation pipeline (feature/translation@HEAD):

1. Onboarding engine page now hosts a translation row.
   APISetupPage renders the same TranslationPickerRow used in the
   language tab, so first-time users can pick a target language
   before they ever see the keyboard. Same persisted bindings; same
   'needs cloud' hint when the local engine is active.

2. Local engine hides the provider / API card unconditionally.
   Removed the 'local + cloud polish on → show API fields' branch
   from SettingsView. Provider/base URL/API key/model controls have
   no use in local mode (translation is cloud-only anyway), and
   exposing them invited users to fill in a DeepSeek key they
   can't use.

3. 'Cloud polish after ASR' toggle loses its long subtitle.
   The descriptive copy in LocalEngineSettingsRows.cloudPolishRow
   was a wall of text that explained things visible elsewhere in
   Settings. Title + switch is enough; the CloudPolishDisclosureBanner
   (rendered by EnginePickerSection when cloud is active) already
   covers the 'this sends text to your API' disclosure.

4. Translation row becomes a single dropdown with a 'Don't
   translate' default.
   TranslationPickerRow replaced with a one-row Menu picker:
   '不翻译 / English / 中文 (简体) / 中文 (繁體) / 日本語 / 한국어 /
   Français / Deutsch / Español / Русский / Português'.
   '不翻译' maps to translationEnabled=false; any locale maps to
   translationEnabled=true + translationTargetLocaleId=<id>.
   TranslationLanguageCatalog gains an 'off' sentinel so the picker's
   single binding stays a plain String.

5. Language tab reorder.
   SettingsView.languageAndModelsSection: ASR locale ('识别语言')
   now sits above the local-models block; translation row sits at
   the bottom. The reading order follows the pipeline direction
   (input → post-processing → post-post-processing).

Localization:
  - 'settings.translation.title' → '翻译' / 'Translation'
  - new 'settings.translation.off' / 'settings.translation.hint.needsCloud'
  - dropped unused subtitle / target-language keys

xcodebuild scheme=OSGKeyboard config=Debug destination=iPhone 17
Simulator: BUILD SUCCEEDED (0 warning, 0 error).

OSGKeyboard/Views/LocalEngineSettingsRows.swift

@@ -57,25 +57,21 @@ struct LocalModelsGroup: View {
     /// itself is always live (the user can flip it without having a
     /// key yet), but the polish call short-circuits with an Alert if
     /// the Keychain is empty when it fires.
+    ///
+    /// v0.2.1: dropped the long descriptive subtitle — it explained
+    /// things the user could read about elsewhere in Settings
+    /// (provider / API key section) and made the row visually heavy.
+    /// Title + switch is enough; details live in `CloudPolishDisclosureBanner`.
     private var cloudPolishRow: some View {
-        VStack(alignment: .leading, spacing: Spacing.xs) {
+        Toggle(isOn: $config.localModeCloudPolishEnabled) {
-            Toggle(isOn: $config.localModeCloudPolishEnabled) {
+            Text("settings.localModels.cloudPolish.title")
-                VStack(alignment: .leading, spacing: 2) {
+                .font(TypeStyle.body)
-                    Text("settings.localModels.cloudPolish.title")
+                .foregroundStyle(palette.textPrimary)
-                        .font(TypeStyle.body)
-                        .foregroundStyle(palette.textPrimary)
-                    Text("settings.localModels.cloudPolish.subtitle")
-                        .font(TypeStyle.caption2)
-                        .foregroundStyle(palette.textTertiary)
-                        .fixedSize(horizontal: false, vertical: true)
-                }
-            }
-            .toggleStyle(.switch)
-            .tint(palette.accent)
         }
+        .toggleStyle(.switch)
+        .tint(palette.accent)
         .padding(.horizontal, Spacing.md)
-        .padding(.vertical, Spacing.sm)
+        .frame(minHeight: SettingsListMetrics.singleLineMinHeight)
-        .frame(minHeight: SettingsListMetrics.doubleLineMinHeight)
     }
 
     // MARK: Helpers

OSGKeyboard/Views/OnboardingView.swift

@@ -756,8 +756,36 @@ private struct APISetupPage: View {
                     }
                     .padding(.horizontal, Spacing.lg)
                 }
+
+                // v0.2.1: translation row lives on the onboarding engine
+                // page so first-time users can pick a target language
+                // before they ever see the keyboard. We render the same
+                // `TranslationPickerRow` used in the language tab — same
+                // persisted bindings, same "需云端" hint when local is
+                // active — wrapped in the section's surface card so it
+                // sits flush with the engine / provider cards above.
+                translationSection
+                    .padding(.horizontal, Spacing.lg)
             }
             .padding(.bottom, Spacing.xxxl)
         }
     }
+
+    private var translationSection: some View {
+        VStack(alignment: .leading, spacing: SettingsListMetrics.sectionLabelSpacing) {
+            Text("settings.translation.title")
+                .font(TypeStyle.caption2)
+                .foregroundStyle(palette.textSecondary)
+                .textCase(.uppercase)
+                .frame(maxWidth: .infinity, alignment: .leading)
+            VStack(spacing: 0) {
+                TranslationPickerRow(config: config)
+            }
+            .background(palette.surface, in: RoundedRectangle(cornerRadius: Radius.large, style: .continuous))
+            .overlay(
+                RoundedRectangle(cornerRadius: Radius.large, style: .continuous)
+                    .stroke(palette.divider, lineWidth: 0.5)
+            )
+        }
+    }
 }

OSGKeyboard/Views/SettingsView.swift

@@ -62,17 +62,16 @@ struct SettingsView: View {
                         VStack(spacing: Spacing.md) {
                             appLanguageSection
                             engineSection
+                            // v0.2.1: hide provider/api card when the
+                            // local engine is active regardless of the
+                            // cloud-polish toggle. Local mode is
+                            // contractually ASR-only, so provider/model/
+                            // base URL/API key controls have no use —
+                            // and exposing them invites the user to fill
+                            // out a DeepSeek key they can't use.
                             if config.engineMode == "cloud" {
                                 providerSection
                                 apiSection
-                            } else if config.localModeCloudPolishEnabled {
-                                // v0.2.0: local engine + cloud polish on.
-                                // Surface the provider / API key fields so
-                                // the user can fill in their DeepSeek key.
-                                // We hide them when the toggle is off so the
-                                // local engine stays genuinely local.
-                                providerSection
-                                apiSection
                             }
                             languageAndModelsSection
                             if config.engineMode == "cloud" {
@@ -128,10 +127,12 @@ struct SettingsView: View {
         VStack(alignment: .leading, spacing: SettingsListMetrics.sectionLabelSpacing) {
             sectionHeader("settings.language.title")
             VStack(spacing: 0) {
-                if config.engineMode == "local" {
+                // v0.2.1: language tab reorder — ASR locale ("识别语言")
-                    LocalModelsGroup(config: config)
+                // now sits above the cloud-polish toggle / local models
-                    Divider().background(palette.divider)
+                // block so the row that maps to microphone input comes
-                }
+                // first, the row that maps to post-processing comes
+                // second, and translation (post-post-processing) sits at
+                // the bottom.
                 LocalePickerRow(
                     locales: effectiveLocales,
                     selection: Binding(
@@ -139,11 +140,10 @@ struct SettingsView: View {
                         set: { config.localeId = $0 }
                     )
                 )
-                // v0.2.1: translation toggle + target-language picker.
+                if config.engineMode == "local" {
-                // Sits at the bottom of the language section so the user
+                    Divider().background(palette.divider)
-                // finds it next to the ASR locale it complements. Reuses
+                    LocalModelsGroup(config: config)
-                // `config.translationEnabled` / `config.translationTargetLocaleId`
+                }
-                // bindings — no new state, no new persistence path.
                 Divider().background(palette.divider)
                 TranslationPickerRow(config: config)
             }

OSGKeyboard/Views/TranslationPickerRow.swift

@@ -1,22 +1,23 @@
 // TranslationPickerRow.swift
 // OSGKeyboard · Main App
 //
-// List row that hosts the translation toggle + target-language picker.
+// Single-row "翻译" picker — replaces the previous two-row toggle +
-// Lives at the bottom of the language tab in Settings (see
+// target-locale dropdown. Lets the user pick "不翻译" (off, the
-// `SettingsView.languageAndModelsSection`) so it sits right next to
+// default) or one of the 10 target languages, all from a single
-// the existing ASR locale picker — same picker family, same row
+// `Menu`.
-// metrics.
 //
-// Layout:
+// Mapping to persisted state:
-//   • First row  → switch (label on the left, switch on the right)
+//   • "不翻译"            → translationEnabled = false
-//   • When on    → a second row with a Menu picker for the target
+//   • any specific locale → translationEnabled = true, translationTargetLocaleId = <id>
-//     language. Disabled when the local engine is active so the user
-//     immediately sees why the picker is greyed out (instead of picking
-//     a target that the pipeline silently ignores).
 //
-// Reuses the host app's `ProviderConfig` `translationEnabled` /
+// The local engine constraint ("translation is cloud-only") is handled
-// `translationTargetLocaleId` bindings — no new state, no new
+// in two places that read this row:
-// persistence path.
+//   • The picker greys out specific locales (and prepends a "需云端"
+//     hint) when `config.isLocalEngine` — the user can still pick
+//     something but it won't fire end-to-end until they switch engines.
+//   • The pipeline (`PolishingService`) rejects `.translate` on local
+//     engine with `translationNotAvailable`, which `KeyboardViewController`
+//     surfaces as a 2.4s toast. Belt + suspenders.
 
 import SwiftUI
 import OSGKeyboardShared
@@ -26,90 +27,87 @@ struct TranslationPickerRow: View {
     @ObservedObject var config: ProviderConfig
 
     var body: some View {
-        VStack(spacing: 0) {
-            toggleRow
-            if config.translationEnabled {
-                Divider().background(palette.divider)
-                targetRow
-            }
-        }
-    }
-
-    private var toggleRow: some View {
         HStack {
-            VStack(alignment: .leading, spacing: 2) {
+            Text("settings.translation.title")
-                Text("settings.translation.title")
-                    .font(TypeStyle.body)
-                    .foregroundStyle(palette.textPrimary)
-                Text(subtitleKey)
-                    .font(TypeStyle.caption2)
-                    .foregroundStyle(palette.textSecondary)
-            }
-            Spacer()
-            Toggle(
-                "",
-                isOn: Binding(
-                    get: { config.translationEnabled },
-                    set: { config.translationEnabled = $0 }
-                )
-            )
-            .labelsHidden()
-            .tint(palette.accent)
-        }
-        .padding(.horizontal, Spacing.md)
-        .frame(minHeight: SettingsListMetrics.singleLineMinHeight)
-    }
-
-    /// Subtitle explains why the toggle is functionally inert when the
-    /// local engine is on. We still let the user flip the toggle in
-    /// that case so their preference is saved — the moment they switch
-    /// back to cloud, translation just works.
-    private var subtitleKey: LocalizedStringKey {
-        config.isLocalEngine
-            ? "settings.translation.subtitle.needsCloud"
-            : "settings.translation.subtitle"
-    }
-
-    private var targetRow: some View {
-        HStack {
-            Text("settings.translation.target")
                 .font(TypeStyle.body)
                 .foregroundStyle(palette.textPrimary)
             Spacer()
             Menu {
                 ForEach(TranslationLanguageCatalog.all) { language in
                     Button {
-                        config.translationTargetLocaleId = language.id
+                        apply(language)
                     } label: {
-                        if language.id == config.translationTargetLocaleId {
+                        if currentSelectionId == language.id {
-                            Label(language.nativeName, systemImage: "checkmark")
+                            Label(displayLabel(for: language), systemImage: "checkmark")
                         } else {
-                            Text(language.nativeName)
+                            Text(displayLabel(for: language))
                         }
                     }
                 }
             } label: {
                 HStack(spacing: 6) {
-                    Text(currentTargetName)
+                    Text(currentLabel)
                         .font(TypeStyle.body)
                         .foregroundStyle(pickerForeground)
+                    if config.isLocalEngine && !currentIsOff {
+                        // Inline hint so the user knows the picker
+                        // selection is being held but won't fire on the
+                        // local engine.
+                        Text("settings.translation.hint.needsCloud")
+                            .font(TypeStyle.caption2)
+                            .foregroundStyle(palette.warning)
+                    }
                     Image(systemName: "chevron.up.chevron.down")
                         .font(.system(size: 11, weight: .bold))
                         .foregroundStyle(palette.textTertiary)
                 }
             }
-            .disabled(config.isLocalEngine)
-            .opacity(config.isLocalEngine ? 0.5 : 1.0)
         }
         .padding(.horizontal, Spacing.md)
         .frame(minHeight: SettingsListMetrics.singleLineMinHeight)
     }
 
-    private var currentTargetName: String {
+    // MARK: - Selection plumbing
-        TranslationLanguageCatalog.resolve(config.translationTargetLocaleId).nativeName
+
+    /// Currently selected id derived from `translationEnabled`. We
+    /// route everything through the `translationEnabled` boolean so the
+    /// picker stays in lock-step with the rest of the system (chip,
+    /// pipeline, `isTranslationEffective`).
+    private var currentSelectionId: String {
+        config.translationEnabled
+            ? config.translationTargetLocaleId
+            : TranslationLanguageCatalog.offLocaleId
+    }
+
+    private var currentLabel: String {
+        displayLabel(for: TranslationLanguageCatalog.resolve(currentSelectionId))
+    }
+
+    private var currentIsOff: Bool {
+        TranslationLanguageCatalog.isOff(currentSelectionId)
+    }
+
+    private func displayLabel(for language: TranslationLanguage) -> String {
+        if language.id == TranslationLanguageCatalog.offLocaleId {
+            return AppL10n.string("settings.translation.off")
+        }
+        return language.nativeName
     }
 
     private var pickerForeground: Color {
-        config.isLocalEngine ? palette.textTertiary : palette.textSecondary
+        currentIsOff ? palette.textSecondary : palette.textPrimary
+    }
+
+    /// Translates a picker choice into the underlying
+    /// `translationEnabled` + `translationTargetLocaleId` pair. Picking
+    /// "不翻译" clears the toggle; any locale flips it on and stores
+    /// the id.
+    private func apply(_ language: TranslationLanguage) {
+        if language.id == TranslationLanguageCatalog.offLocaleId {
+            config.translationEnabled = false
+            return
+        }
+        config.translationEnabled = true
+        config.translationTargetLocaleId = language.id
     }
 }

OSGKeyboard/en.lproj/Localizable.strings

@@ -109,10 +109,9 @@
 "settings.api.title" = "API";
 "settings.language.title" = "Language";
 // v0.2.1: translation feature
-"settings.translation.title" = "Translate after dictation";
+"settings.translation.title" = "Translation";
-"settings.translation.subtitle" = "Send the transcript to your LLM with a translate-and-polish prompt before inserting.";
+"settings.translation.off" = "Don't translate";
-"settings.translation.subtitle.needsCloud" = "Requires the cloud engine — currently disabled.";
+"settings.translation.hint.needsCloud" = "Needs cloud";
-"settings.translation.target" = "Target language";
 "settings.languageModels.title" = "Language & models";
 "settings.localModels.title" = "On-device models";
 "settings.localModels.speechRole" = "Speech";

OSGKeyboard/zh-Hans.lproj/Localizable.strings

@@ -109,10 +109,9 @@
 "settings.api.title" = "接口";
 "settings.language.title" = "语言";
 // v0.2.1: 翻译功能
-"settings.translation.title" = "语音转文字后翻译";
+"settings.translation.title" = "翻译";
-"settings.translation.subtitle" = "将转写文本发送给已配置的 LLM，使用翻译+润色 prompt 处理后插入。";
+"settings.translation.off" = "不翻译";
-"settings.translation.subtitle.needsCloud" = "需开启云端引擎，当前为本地模式暂不生效。";
+"settings.translation.hint.needsCloud" = "需云端";
-"settings.translation.target" = "目标语言";
 "settings.languageModels.title" = "语言与模型";
 "settings.localModels.title" = "本地模型";
 "settings.localModels.speechRole" = "语音识别";

OSGKeyboardShared/Models/TranslationLanguage.swift

@@ -28,12 +28,22 @@ public struct TranslationLanguage: Identifiable, Hashable, Sendable {
 }
 
 public enum TranslationLanguageCatalog {
-    /// Default target language id used on fresh installs.
+    /// Sentinel id for "don't translate" — the default selection in the
+    /// picker. Picked over an `Optional<TranslationLanguage>` so the
+    /// single-row `Picker` binding stays a plain `String` (and the same
+    /// code path also works for the `TranslationChip` Menu).
+    public static let offLocaleId = "off"
+    /// Default target language id used on fresh installs when translation
+    /// is enabled. The picker still defaults to `offLocaleId` — this is
+    /// only the language we'd fall back to if a stale "on" state is
+    /// recovered without a remembered target.
     public static let defaultLocaleId = "en"
 
     /// Curated set. Order matters — the picker / chip render top-to-
-    /// bottom, and `defaultLocaleId` is the default selection.
+    /// bottom, with `offLocaleId` ("不翻译") at the very top so the
+    /// "turn off" action is one tap away from any enabled state.
     public static let all: [TranslationLanguage] = [
+        TranslationLanguage(id: offLocaleId, promptLanguageName: "", nativeName: ""),
         TranslationLanguage(id: "en",    promptLanguageName: "English",  nativeName: "English"),
         TranslationLanguage(id: "zh-Hans", promptLanguageName: "Simplified Chinese", nativeName: "简体中文"),
         TranslationLanguage(id: "zh-Hant", promptLanguageName: "Traditional Chinese", nativeName: "繁體中文"),
@@ -46,14 +56,23 @@ public enum TranslationLanguageCatalog {
         TranslationLanguage(id: "pt",    promptLanguageName: "Portuguese", nativeName: "Português"),
     ]
 
+    /// True when the given id is the "off" sentinel. Used by the picker
+    /// to flip `translationEnabled` and by the pipeline to skip the
+    /// translate prompt.
+    public static func isOff(_ id: String) -> Bool {
+        id == offLocaleId
+    }
+
     /// Resolve a stored locale id to its catalog entry. Falls back to
-    /// `defaultLocaleId` when the id is missing or unknown — matches the
+    /// `offLocaleId` (the picker default) when the id is missing or
-    /// pattern used elsewhere (e.g. `ASRLocaleLabels`) so the keyboard
+    /// unknown — matches the pattern used elsewhere (e.g.
-    /// never crashes on a stale persisted value.
+    /// `ASRLocaleLabels`) so the keyboard never crashes on a stale
+    /// persisted value, and the picker lands on the safe "off" state
+    /// instead of an arbitrary language.
     public static func resolve(_ id: String) -> TranslationLanguage {
         if let match = all.first(where: { $0.id == id }) {
             return match
         }
-        return all.first { $0.id == defaultLocaleId } ?? all[0]
+        return all.first { $0.id == offLocaleId } ?? all[0]
     }
 }