chore: drop iOS 18–25 / non-iPhone support, require iOS 26

Two related cleanups the user asked for in one shot:

1. iPhone-only is now enforced at every target — Mac Catalyst and
   visionOS were never configured in `project.yml`, but the
   `OSGKeyboardShared` framework and the two test bundles were
   still defaulting to `TARGETED_DEVICE_FAMILY = "1,2"` (iPhone +
   iPad). All four targets now explicitly set `"1"`. SDK is
   `iphoneos` for everyone, no `xros` / `macosx`.

2. Deployment target bumped from iOS 18.0 to iOS 26.0 across the
   board (`project.yml` + the ext's per-target setting). With
   iOS 26 as the floor, the iOS 18–25 SFSpeechRecognizer path
   became dead code and several `#available` checks became
   always-true. Removed:

   - `AppleSpeechASR` (the entire SFSpeechRecognizer-based ASR
     backend) and the `#available(iOS 26.0, *)` factory branch.
     `ASRServiceFactory.make()` now returns `SpeechAnalyzerASR()`
     directly. SpeechAnalyzer is always fully on-device, which
     also made the `requiresOnDevice` flag meaningless.
   - `requiresOnDevice` from the `ASRService.transcribe` protocol
     signature, from `ProviderConfig`, `AppGroupStore`,
     `KeyboardState`, `AppGroupPersistor`, and the ext's
     `KeyboardViewController` (`state.requiresOnDevice`,
     `state.setRequiresOnDevice`, `persistRequiresOnDevice`).
   - `#available(iOS 17.0, *)` branch in
     `PreviewASRController.requestMicrophonePermission` and the
     ext's `PermissionManager.requestMicPermission` — both now
     just call the iOS 17+ `AVAudioApplication` API directly.
   - The `else` (iOS 18–25) branch in `SettingsView.asrEngineRow`
     — the on-device-only toggle is gone, the row is a static
     "SpeechAnalyzer active" badge. Same for the `else` branch
     in `EnginePickerSection.localSubtitle`.
   - `makeMicAuthHandler` (the iOS < 17 mic permission callback
     wrapper) from `PreviewASRController`.

   No `#available` / `@available` checks remain in the codebase
   except for the SpeechAnalyzer class itself (now unnecessary
   too, but kept for clarity — `AVAudioApplication` and
   `SpeechAnalyzer` are both iOS 17+ / iOS 26+ respectively,
   and the deployment target of 26 makes the explicit
   `@available` redundant; I left the SpeechAnalyzer class
   un-`@available` and removed the `@available(iOS 26.0, *)`
   decoration since it's no longer needed).

   The Keyboard ext's existing ASRService usage
   (`asr.transcribe(stream:locale:)`) is unchanged at the
   call-site level — just the third argument is gone.

3. Updated `info.plist` UISupportedInterfaceOrientations is
   already `[UIInterfaceOrientationPortrait]` only, which is
   correct for an iPhone-only app; no change needed.

Build: BUILD SUCCEEDED.
Tests: 22/22 pass.
Verified: `TARGETED_DEVICE_FAMILY = 1` on all four targets,
`SDKROOT = iphoneos` on all four.

🤖 Generated with Claude Code

OSGKeyboardShared/Models/ProviderConfig.swift

@@ -26,7 +26,6 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
         static let systemPrompt    = "config.systemPrompt"
         static let modeId          = "config.modeId"
         static let localeId        = "config.localeId"
-        static let requiresOnDevice = "config.requiresOnDevice"
         static let engineMode       = "config.engineMode"
     }
 
@@ -62,11 +61,6 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
     @Published public var localeId: String {
         didSet { defaults.set(localeId, forKey: Key.localeId) }
     }
-    /// When `true`, forces SFSpeechRecognizer to on-device only mode.
-    /// Ignored on iOS 26+ where SpeechAnalyzer is always on-device.
-    @Published public var requiresOnDevice: Bool {
-        didSet { defaults.set(requiresOnDevice, forKey: Key.requiresOnDevice) }
-    }
     /// "local" → on-device ASR only, no LLM polishing.
     /// "cloud" → ASR + LLM polish (default).
     @Published public var engineMode: String {
@@ -109,7 +103,6 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
             ?? AppGroupStore.defaultSystemPrompt(for: pid)
         self.modeId          = defaults.string(forKey: Key.modeId)     ?? "polish"
         self.localeId        = defaults.string(forKey: Key.localeId)   ?? "auto"
-        self.requiresOnDevice = defaults.bool(forKey: Key.requiresOnDevice)
         self.engineMode       = defaults.string(forKey: Key.engineMode) ?? "cloud"
     }