The supervisor health-polls /internal/engine-state every couple seconds. While the
engine is GIL-busy generating, that poll can't be answered in time and the engine
was flipped to healthy=False — flapping out of the UI/routing mid-generation even
though it's perfectly alive. Now a poll timeout only downgrades health when the
PROCESS IS GONE (true death, already caught by the restart check); a timeout with
the process alive keeps the last-known-healthy state. Also bump proxy_status_timeout
2s→4s so transient GIL contention doesn't trip it. (Pairs with the engine-state
VRAM cache that removed the per-poll CUDA call.)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>