fix: recover dead FFmpeg senders and add iframe login
Arena maintenance
1a38430
Run the sender watchdog on every manager pass, detach stopped supervisors, protect detailed health, restore the dashboard, pin dependencies, and add regression coverage.
Keep the YouTube FFmpeg session across TikTok silence by splicing a new FLV.
Measured on On @aboodi1994: FLV went silent ~12s, FFmpeg died, YouTube
spun, then the same FLV was retried. HLS reconnects inside FFmpeg.
FLAP_LIMIT 2 so PK layout changes stick to a constant canvas sooner.
Do not end the supervisor Event on FFmpeg teardown.
_teardown used stop.set() to wake the pump; sender_loop treated that as
account stop, occupied a new FFmpeg, and flashed YouTube. Stall still
kills the process via force_stop; the thread reconnects on the same slot.
Sync full Tktktk engine (relay-v2.9-confirm) onto this Space.
Independent per-broadcaster relays, concurrency cap 5, confirm-before-exit
on idle offline, tests included. Space identity (title On) kept. Do not
enable OAuth automation here and on Tktktk against the same YouTube channel.
