fix: force-reset audio engine on silent capture

Author: jatinkrmalik

Sources/VocaMac/Models/AppState.swift

@@ -613,6 +613,8 @@ final class AppState: ObservableObject {
 
         guard audioData.contains(where: { abs($0) >= 0.0001 }) else {
             cursorOverlay.hide()
+            // Don't keep a capture route that only produced silence warm.
+            audioEngine.forceReset()
             let message = "No microphone audio detected. If your MacBook lid is closed, select an external microphone in Settings → Audio."
             VocaLogger.warning(.appState, message)
             showTemporaryError(message)

Tests/VocaMacTests/AppStateRecordingTests.swift

@@ -130,6 +130,8 @@ final class AppStateRecordingTests: XCTestCase {
         XCTAssertTrue(appState.errorMessage?.contains("external microphone") == true)
         XCTAssertNil(mocks.whisperService.lastTranscribedAudioData)
         XCTAssertEqual(mocks.textInjector.injectCallCount, 0)
+        XCTAssertEqual(mocks.audioEngine.forceResetCallCount, 1,
+                       "Silent capture should force-reset the engine so a dead route is not kept warm")
     }
 
     func testSelectedModelSizeDefault() {