chore(release): bump version to 2.1.6 (build 131)

Version: CURRENT_PROJECT_VERSION 130 -> 131 (project.yml, AGENTS.md, READMEs,
docs/llms.txt).

fix(flow): host-app identification now compiles in every build configuration
(Debug, TestFlight, Release). The arbiter probe and HostAppIdentity were
DEBUG-only, so TestFlight/App Store builds never knew the host bundle id and
could not auto-return after a startflow handoff. Debug-only logging and the
Home test card are unchanged.

Also includes the pending work in the tree:
- Home: single account/setup card surface (HomeAccountSurfacePolicy/Views)
- Wide screens: voice key row and centred mic placement, iPhone Duo layout
- Keyboard: clipboard skill ranking and AI skill layout updates
- Debug: account session handoff to the Simulator (+ import script)
- Docs: portfolio assets, privacy policy URL, site/README refresh

OSGKeyboardTests/AIHintKeywordExtractorTests.swift

@@ -182,6 +182,64 @@ final class AIClipboardSkillTests: XCTestCase {
         )
     }
 
+    func testTranslateToTargetUsesConfiguredTargetLanguage() {
+        let prompt = AIClipboardSkillCatalog.instruction(
+            skillID: AIClipboardSkillCatalog.translateToTargetID,
+            locale: "en",
+            translationTargetLocaleId: "ja",
+            preferredLanguages: ["zh-Hans"]
+        )
+        XCTAssertTrue(prompt.contains("Japanese"))
+        XCTAssertFalse(prompt.contains("Chinese"))
+    }
+
+    func testTranslateToTargetPromptFallsBackWhenTargetIsOff() {
+        let prompt = AIClipboardSkillCatalog.instruction(
+            skillID: AIClipboardSkillCatalog.translateToTargetID,
+            locale: "en",
+            translationTargetLocaleId: TranslationLanguageCatalog.offLocaleId
+        )
+        XCTAssertTrue(prompt.contains("English"))
+    }
+
+    func testTranslateToTargetButtonTitleNamesTargetAndHidesWhenOff() {
+        XCTAssertEqual(
+            AIClipboardSkillCatalog.translateToTargetButtonTitle(
+                translationTargetLocaleId: "en",
+                uiLanguage: .chinese
+            ),
+            "翻译英语"
+        )
+        XCTAssertEqual(
+            AIClipboardSkillCatalog.translateToTargetButtonTitle(
+                translationTargetLocaleId: "ja",
+                uiLanguage: .english
+            ),
+            "To Japanese"
+        )
+        XCTAssertNil(
+            AIClipboardSkillCatalog.translateToTargetButtonTitle(
+                translationTargetLocaleId: TranslationLanguageCatalog.offLocaleId,
+                uiLanguage: .english
+            )
+        )
+    }
+
+    func testPolishKeepsOriginalLanguageAndCarriesNeverAnswerBoundary() throws {
+        let skill = try XCTUnwrap(
+            AIClipboardSkillCatalog.skill(id: AIClipboardSkillCatalog.polishOriginalID)
+        )
+        let prompt = AIClipboardSkillCatalog.instruction(
+            for: skill,
+            locale: "en",
+            translationTargetLocaleId: "ja"
+        )
+        XCTAssertTrue(prompt.contains("without changing its language"))
+        XCTAssertTrue(prompt.contains("grammar"))
+        XCTAssertTrue(prompt.contains("Non-negotiable boundary"))
+        XCTAssertFalse(prompt.contains("Japanese"))
+    }
+
     func testSummarizeAsksForOverviewNotShortening() {
         let prompt = AIClipboardSkillCatalog.instruction(
             skillID: AIClipboardSkillCatalog.summarizeID,