Implement on-device iOS text-to-speech using AVSpeechSynthesizer,
mirroring the Android native TextToSpeech plugin so the shared
NativeTTSClient drives both platforms through the same command and
tts_events contract.
- Swift NativeTTSPlugin: speak/stop/pause/resume/rate/pitch/voice and
voice enumeration, with region-disambiguated duplicate voice names and
a small preUtteranceDelay to avoid first-word clipping.
- Enable the native TTS client on iOS in TTSController.
- Make TTS teardown resilient: reset UI state up front and tear down the
controller, media session, and background audio in parallel so a slow
native shutdown can never leave the TTS icon or lock-screen session
stuck on.
- Keep iOS on navigator.mediaSession for the lock screen (Android uses
the native foreground service), which restores the Edge TTS cover and
current-sentence metadata.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Huang Xin