Guard handleTTSSpeak with a single-flight ref so a second tts-speak
event that arrives while the first is still inside its initial awaits
(initMediaSession / backgroundAudio / TTSController.init) is ignored
instead of racing ahead to construct a second TTSController. Without
this, rapid clicks produced two concurrent speakers talking over each
other because viewState.ttsEnabled is only set at the end of the first
invocation, so the footer bar would dispatch tts-speak twice.
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Huang Xin
b679817fce