webcam copy

docs/pt2-protocol.md

@@ -646,6 +646,25 @@ The gated scenario first seeds candidate secondary-table feature bits with comma
 
 Then it streams `E000[0x008F]=0x1800` and `E000[0x0093]=0x90FF`. This is the better next watch if quiet/broad E000-only refreshes do not produce local-control TX.
 
+## Bench Webcam Capture
+
+For tests where LCD timing/state matters, `serial_scenario.py` can take webcam
+snapshots tied to exact TX commands. Current bench calibration:
+
+```powershell
+--camera-index 4 --snapshot-delays 0.5
+```
+
+Camera index `4` is the working panel-facing webcam on the current PC. A single
+`0.5` second post-TX delay captures readable LCD changes without creating the
+large image sets produced by `0,0.25,1.0`.
+
+Example:
+
+```powershell
+.\.venv\Scripts\python.exe scripts\serial_scenario.py scenarios\copy-step-006d-006c-1000ms.json --parity E --quiet-console --log captures\copy-webcam.txt --result-json captures\copy-webcam-result.json --snapshot-dir captures\copy-webcam-shots --camera-index 4 --snapshot-delays 0.5
+```
+
 After a run, summarize unexpected device frames with:
 
 ```powershell