open() now hands the keepalive BACK on failure (the WGC attach_keepalive pattern) so the caller can fall back instead of tearing the virtual display down. Added a bounded wait_for_attach() that polls the driver's DRV_STATUS_OPENED — it checks ATTACH status, not frame arrival, so it never false-fails on an idle desktop that has composed no frame yet.
An attach failure (e.g. a hybrid-GPU render mismatch -> DRV_STATUS_TEX_FAIL, or the driver never opening the ring within 4s) now fails open() -> capture.rs falls back to DDA, instead of next_frame's 20s deadline leaving the session black. Pairs with the driver SET_RENDER_ADAPTER fix (0a7ae5e).
Verified: host clippy (nvenc) clean on the RTX box. Behavioral validation (fallback trigger + happy-path attach timing) needs an on-glass session.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
ed583650a6