docs: note the webcam/video wall-clock timers in CLAUDE.md

TrackLab's raw setTimeout/setInterval (camera init, FPS sampling, source
debounce) track hardware time, not the sim clock — documented-allowed
deviations from CONVENTIONS.md §2.9; record them per §7.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: veillette

CLAUDE.md

@@ -36,6 +36,7 @@ Follows the shared [OpenPhysics accessibility convention](https://github.com/Ope
 
 - OpenCV WASM requires COOP/COEP headers (configured in Vite dev + production)
 - Sample videos in `public/videos/`
+- **Wall-clock timers (allowed exception)** — the webcam/video code uses raw `setTimeout`/`setInterval` rather than `stepTimer`: a camera-init timeout in `webcam.ts`, the FPS-sampling interval in `track-lab/view/WebcamPanel.ts`, and a source-switch debounce in `track-lab/view/VideoSourceControlNode.ts`. These track real hardware/wall-clock time (independent of the sim clock), so they are the documented exceptions to the "no `setTimeout`/`setInterval`" rule (CONVENTIONS.md §2.9 / §7).
 
 ## Testing