Fix stalled Continue Watching source recovery

[d1same]

What changed

• treat Android READY as prepared, not established playback, so frozen resumes keep the fast startup watchdog
• poll live source health on web and native playback and promptly advance confirmed blocked releases
• retry an unknown stall once at the same episode/timestamp, then change to another ranked release without visiting details or advancing episodes
• hedge two replacement candidates so one stalled alternate cannot block recovery serially
• align release identities at 2.8.1 and document the recovery contract

Verification

• npm.cmd test: 441/441 passed
• npm.cmd run verify:full: passed
• Android lint, unit tests, debug build: passed
• Android emulator stress: 0 failures, 0 warnings
• desktop 1280x720 and mobile 390x844 visual smoke: no console errors/warnings or overflow