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>

common/params.cc

@@ -416,6 +416,7 @@ std::unordered_map<std::string, uint32_t> keys = {
     {"ScreenBrightnessOnroad", PERSISTENT},
     {"ScreenManagement", PERSISTENT},
     {"ScreenRecorder", PERSISTENT},
+    {"ScreenRecorderDebug", PERSISTENT},
     {"ScreenTimeout", PERSISTENT},
     {"ScreenTimeoutOnroad", PERSISTENT},
     {"SearchInput", PERSISTENT},