Recording not stopped when recorder disconnects (headless Chromium leak)

[hweihwang]

Steps to reproduce

1. Create a new whiteboard
2. Start recording; draw a bit
3. Close the whiteboard tab while recording

Actual

• Recording process (headless Chromium) keeps running on server
• Recording entry persists; reopening shows recording in progress

Expected

• When the recorder leaves (last socket for user), recording stops and cleans up
• Recording state cleared for room/user

Impact

• Orphaned Chromium processes; resource leak
• User stuck in recording until manual stop

Suspected cause

• RoomLifecycleService.onDisconnecting ends presentation but does not handle recordings
• Only explicit stop-recording stops recording; no unload/leave hook
• Sweeper only clears dead nodes, not normal disconnect
• tests/integration/multinode-redis.spec.mjs currently assumes recordings persist across disconnect

Possible fix

• On disconnecting, if recorder has no other sockets in room, trigger recording stop (local or forwarded) and remove entry
• Update tests to reflect expected stop-on-leave behavior