Keep media playing through headset standby

Real-Frame testing (2026-09-29) found an unworn headset enters standby
within seconds; SetOverlayRaw then returns RequestFailed (23) and the
movie died. The player now drops frames during standby, keeps audio
and pacing, re-sends stills and the theatre surround after waking, and
only errors after five minutes without an accepted frame.

A Stop arriving while the player is already shutting down is ignored,
so a finished video stays 'ended' instead of 'error: Stopped'. The
status now reports the layout's real source (filename/metadata).

Docs record the end-to-end device matrix (API, web UI, CLI).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/vr-video.md

@@ -75,6 +75,34 @@ All test media were generated by us. No paid content or DRM was involved.
 
 ![Our Gaussian-splat stereo preview on the Frame](img/media-splat-proof.png)
 
+**Verified end to end, 2026-09-29** (same build; headset unworn): uploads
+through the HTTP API, the web UI and `scripts/push-vr-video.sh`, all played by
+the owned player. Our generated test files:
+
+| Case | Result |
+|---|---|
+| H.264 half-SBS 1920×1080 with AAC, theatre | 240/240 frames in 8.09 s; audio stream "Frame Control Media" in PulseAudio |
+| H.265 half-OU 1920×1080 | 180/180 frames in 6.03 s; red left eye, cyan right |
+| H.264 full-SBS 3840×1080, `stereo_mode=left_right` only | Detected from metadata; 150/150 frames in 5.03 s |
+| H.264 1280×720, explicit 2D | 150/150 frames in 5.02 s |
+| SBS PNG, OU JPEG (theatre) | Correct eye in each capture |
+| 3,000-Gaussian `.splat` | Rendered in about 5 s, then held until Stop |
+| 2D file on Auto, `_SBS_OU` file, HEIC, VP9 | Refused with the documented message |
+| Second Play while one runs | Refused: "Stop the current media…" |
+
+Stop always left the unit inactive, and no player process remained.
+
+**Standby (verified):** an unworn Frame turns its displays off a few seconds
+after it wakes. `SetOverlayRaw` then returns `RequestFailed` (23). The
+first run's movie died there. The player now drops frames while the headset
+is in standby, keeps the audio and its clock going, and resumes the picture
+when the headset wakes. The 8 s movie above dropped 40 frames and finished.
+Stills and the theatre surround are re-sent after waking. Five minutes
+without an accepted frame is reported as an error. Headset-view captures
+taken during standby show a flat dark frame, not our screen.
+
+![Media panel in Frame Control while a photo plays on the Frame](img/media-ui-panel.png)
+
 **Verified failed route:** GStreamer 1.24.2's `playbin` selected
 `v4l2h264dec`, delivered the first RGBA sample and then segfaulted (exit 139)
 in the basic appsink probe and the OpenVR probe. We do not ship that route.