- Multi-audio items now ship every audio track as an HLS rendition in one session
(stream.py var_stream_map -> master.m3u8), so hls.js switches audio CLIENT-SIDE with
no ffmpeg restart, same timeline, no gap/drift. /session gains ?multi=1 (forces HLS
even for direct-playable multi-audio files); K is probed from the video variant seg.
- Restore the selected audio track on AUDIO_TRACKS_UPDATED, not MANIFEST_PARSED (the
renditions aren't parsed yet on MANIFEST_PARSED, so the set was dropped -> after F5 the
UI showed the restored track but playback stayed on the default).
- Resume position now survives F5: a pagehide keepalive beacon (plexProgressBeacon)
saves the current position on reload/close/navigate, since React effect cleanup does
not run on a full reload; seekTo writes the target into absRef immediately so a save
right after a seek is accurate.