New mediaSession.ts wraps the standard Media Session API - shared by
Player.ts and MusicBar.ts, which can never both be active at once so
there is no risk of them fighting over this one global. Metadata/
position/playback-state hook into each players own existing single
source of truth (updatePlayPauseBtn/updateProgressBar, setPlayIcon/
updatePositionDisplay) instead of adding parallel call sites. Play/
pause/seek are wired once and read isHost/conn fresh on every
OS-triggered call, so they keep working through a live host handoff;
a non-host play/pause routes through the same requestPause/
requestResume the request toolbar already uses, and seek is gated on
isHost the same way the in-page seek bar already is. Next is handled
separately since a registered nexttrack handler is what makes the OS
show that control at all - its presence tracks whatever the in-page
equivalent already tracks (isHost && hasNextQueued for video, a vote
skip for music). Cleared entirely on leaving a party/page, or just to
idle (metadata/state only) when a listen partys queue runs empty but
the party itself is still open.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
