b9b362189b
Live confirmation on worker-3: the flash was Mutter's CORRUPTED, size-0 cursor-update buffers (chunk_flags=CORRUPTED) carrying recycled old frames — drained=1 always, so latest-frame-only draining wasn't the lever, the CORRUPTED skip was (OBS issue 8630). Demote the verbose drain diagnostic to a rate-limited debug line and document the root cause inline. Validated: zero-copy back on GNOME (dmabuf->CUDA, 5120x1440) AND flash-free with FORCE_SHM off. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>