Add GoPro client notes to AGENTS.md: Xbox mapping, QR view, sidecar IDs

AGENTS.md

@@ -233,6 +233,35 @@ setInterval(() => {
   4. If no beacon is received for ~30–60 s, mark the device offline.
 - The IP in the beacon is what the listener should use for all subsequent HTTP API calls.
 
+## GoPro Client (`clients/gopro-scicam/`)
+
+Flask-based USB controller for GoPro HERO12. Serves web UI on port 5000, captures download to local `captures/` with JSON sidecars.
+
+### Xbox Controller Mapping (Browser Gamepad API)
+
+Tested with "Microsoft X-Box 360 pad" on Linux (`/dev/input/js0`).
+**Note:** Standard mapping (`gp.mapping === 'standard'`) button indices differ from X-input labels:
+
+| Button Index | Physical Label | Action |
+|--------------|----------------|--------|
+| 0 | A | Capture photo |
+| 1 | B | Toggle QR display overlay |
+| 2 | X | Capture photo |
+| 3 | Y | **Next Box** (regenerate `item_id`) |
+
+### QR View (`--qrview`)
+
+- Spawns a borderless Tkinter window on DP-1 (`1920x1080+0+0`)
+- Displays the current `item_id` as a maximized QR code
+- Polls for UUID changes every 500ms and redraws with green flash
+- Left-click or `N` key = regenerate box ID
+- Right-click or `Q`/`Escape` = close window
+
+### Sidecar ID Model
+
+- `item_id`: single point of truth — the QR visible in the photo (either detected from image or current box ID fallback)
+- `capture_id`: unique UUID generated per individual photo/video
+
 ## Future Roadmap (do not break)
 
 - **Database sync** is planned. It must be non-destructive to images/sidecars.