On the first song after a fresh load on desktop, the audio engine is often
still starting when the song loads, so the song begins on the HTML5 <audio>
element and the engine-reroute watcher then migrates it to the JUCE backing
transport. The reroute's first step is a deliberate audio.pause(), which
rejects autoplay's in-flight togglePlay() audio.play() with an AbortError —
even though playback continues on JUCE.
togglePlay()'s catch then reset isPlaying=false and the button to "Play"
while the song kept playing: the button showed Play during playback, so it
took two clicks to actually pause (one to resync the flag, one to pause).
The reroute already guards the <audio> 'play'/'pause' DOM listeners with
window._juceRerouteInProgress; this extends the same guard to togglePlay()'s
catch and the count-in catch, so a play() rejection caused by the reroute's
own pause doesn't clobber the button. A genuine failure (outside a reroute)
still resets correctly.
Adds a regression test that drives togglePlay() through a reroute-aborted
play() and asserts the button stays Pause; it fails without the guard.
Claude-Session: https://claude.ai/code/session_01QbexxfTt8q2tAn436MqGWF
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
