audio: Media Session API for reliable mobile auto-advance + lock-screen controls
On mobile, auto-advancing to the next track started then stopped immediately: iOS
pauses a programmatic play() with no active media session. Wire navigator.mediaSession
— per-track metadata (title/artist/album/artwork), play/pause/next/prev/seek action
handlers, and playbackState — so the session stays live (continuous playback works) and
the OS shows lock-screen / notification / headset controls. audio-player.js?v=30.
Co-Authored-By: Claude <noreply@…>