The MANIFEST_PARSED listener was registered after loadSource/attachMedia,
so cached manifests could fire the event before the listener was set —
meaning tryAutoplay never ran. Fix: register the listener first, then
call loadSource. Also switch MP4 and native-HLS paths to play on
loadedmetadata (not immediately after load()) which is the earliest
safe moment to call play(). Belt-and-suspenders canplay fallback now
also explicitly mutes before calling play().
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>