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/ui/ui.h

@@ -231,6 +231,7 @@ typedef struct UIScene {
   bool road_name_ui;
   bool rotating_wheel;
   bool screen_recorder;
+  bool screen_recorder_debug;
   bool show_aol_status_bar;
   bool show_cem_status_bar;
   bool show_jerk;