Only offer video capture devices as webcams (#6732)

* Only offer video capture devices as webcams

V4L2 exposes raw processing and output-only nodes beside usable cameras. The webcam picker and automatic recorder selection treated the first /dev/video node as a camera, so IPU6 laptops opened a black overlay instead of their loopback capture device.\n\nShare one device lister across detection, selection, and recording, and keep only groups whose first video node advertises Video Capture in Device Caps. Cover raw IPU nodes, ordinary capture devices, and capture-less systems.

* Fall through to a later capture-capable node in a webcam group

A group whose first video node is not capture-capable vanished entirely,
even when a later node in the same group could capture. Probe each node
until one qualifies, still emitting at most one device per group. Also
exit zero explicitly: a trailing filtered device used to leak the failed
capability check as the script's exit status.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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Co-authored-by: David Heinemeier Hansson <david@hey.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bin/omarchy-capture-screenrecording

@@ -64,7 +64,7 @@ start_webcam_overlay() {
 
   # Auto-detect first available webcam if none specified
   if [[ -z $WEBCAM_DEVICE ]]; then
-    WEBCAM_DEVICE=$(v4l2-ctl --list-devices 2>/dev/null | grep -m1 "^[[:space:]]*/dev/video" | tr -d '\t')
+    WEBCAM_DEVICE=$(omarchy-capture-webcam-list | sed -n '1s/[[:space:]].*//p')
     if [[ -z $WEBCAM_DEVICE ]]; then
       omarchy-notification-send -u critical -t 3000 "No webcam devices found"
       return 1