'platform' (default): native platform TTS — AVSpeechSynthesizer on iOS,
android.speech.tts.TextToSpeech on Android. Offline, free, quality varies by
installed voices.
'mapbox': Mapbox's cloud speech engine — fetches rendered MP3 audio per
instruction. Higher quality and consistent across platforms, but requires
network connectivity and consumes Mapbox API credits. Falls back to platform
TTS when the network call fails.
TTS playback engine:
'platform'(default): native platform TTS —AVSpeechSynthesizeron iOS,android.speech.tts.TextToSpeechon Android. Offline, free, quality varies by installed voices.'mapbox': Mapbox's cloud speech engine — fetches rendered MP3 audio per instruction. Higher quality and consistent across platforms, but requires network connectivity and consumes Mapbox API credits. Falls back to platform TTS when the network call fails.