Keep a silent looping <audio> element mounted at the app root so macOS
never tears down the CoreAudio session. Without this, backgrounding the
app long enough leaves WaveSurfer's AudioContext in a state where play()
resolves and timeupdate fires, but no audio reaches the output — and not
even cmd+R (full JS reload) restores it, only a full app relaunch.
Uses a zero-PCM WAV blob at full volume rather than a muted element,
since WebKit can optimize muted media away and defeat the purpose.
Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>
