dashcam: re-enable screen recorder, disable training data video

- Re-enable FrogPilot OMX screen recorder (H.264 MP4, 1440x720, 2Mbps)
- Auto-start recording when car is on, auto-stop when off
- Hide all recorder UI elements (invisible to driver)
- Add ScreenRecorderDebug param for bench testing without car
- Disable encoderd (camera .hevc files) — CAN/sensor logs still recorded
- Raise deleter free space threshold from 5GB to 9GB
- Deleter rotates oldest videos before log segments
- Add CLAUDE.md project documentation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/frogpilot/screenrecorder/screenrecorder.cc

@@ -132,13 +132,20 @@ void ScreenRecorder::stop() {
 }
 
 void ScreenRecorder::update_screen() {
-  if (!uiState()->scene.started) {
+  bool car_on = uiState()->scene.started || uiState()->scene.screen_recorder_debug;
+
+  if (!car_on) {
     if (recording) {
       stop();
     }
     return;
   }
-  if (!recording) return;
+
+  // CLEARPILOT: auto-start recording when car is on (or debug flag set)
+  if (!recording) {
+    start();
+    return;
+  }
 
   if (milliseconds() - started > 1000 * 60 * 3) {
     stop();