PlexPlayer's session logic (generation, pending play intent, clock ownership, session offset, reclaim
budget, listener teardown) moves into lib/hlsEngine.ts, a plain class with hls.js behind lib/hlsPort.ts
and its own unit tests.
- A seek, track change or reclaim asked for while a session request is out replaces the queued
target; it is sent once the in-flight answer settles. A burst of 20 presses past the buffer was 20
requests and 20 ffmpeg spawns; it is now 2-3, and plays again ~2 s sooner.
- The player stops its server session when it leaves the item, closes or the page unloads
(POST /api/plex/stream/{rk}/session/{sid}/stop, identity-aware). A left transcode used to run to
the end of the film first.
- A restart asked for after a new session attached but before it played no longer reads the emptied
media as the viewer's pause.
