S4a-4a of the PlexPlayer decomposition. Move audio/subtitle track
selection + subtitle rendering into usePlexTracks: the selected-ordinal
state, change/cycle audio+subtitle, the debounced sub-offset, the audio
A/V-sync offset, and the two subtitle effects (force-showing the mounted
track + positioning cues at the user's subPos). The shared media refs
(video/hls/audio/aoff/abs/multiAudio) stay component-owned and are passed
in, since loadSession + the detail effect write audioRef too; absRef is
hoisted above the hook call for that. No behaviour change; verified by
self-E2E (subtitle on/off via 'S' mounts/removes the <track>, mode
'showing', VTT 804 cues all positioned to line=subPos, subLang persists;
playback uninterrupted). Audio switch is single-track here so cycleAudio
correctly no-ops.
peter
f86313eaa9