dashcamd v3: trip directories, state machine, graceful shutdown

Dashcam recording now organized by trip in /data/media/0/videos/YYYYMMDD-HHMMSS/.
Starts recording immediately on launch (with 10-min idle timer), transitions to
continuous recording when drive gear detected. New trip on every ignition cycle.
Graceful shutdown via DashcamShutdown param with 15s ack timeout in thermald.

- Bitrate reduced to 2500 kbps (was 4 Mbps)
- Trip state machine: IDLE → RECORDING ↔ IDLE_TIMEOUT → TRIP_ENDED
- Deleter: trip-aware deletion (oldest trip first, then segments within active trip)
- camerad changed to always_run (was driverview) so dashcam works offroad
- DashcamShutdown param for graceful close before device power-off

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

selfdrive/thermald/thermald.py

@@ -411,6 +411,16 @@ def thermald_thread(end_event, hw_queue) -> None:
     # Check if we need to shut down
     if power_monitor.should_shutdown(onroad_conditions["ignition"], in_car, off_ts, started_seen):
       cloudlog.warning(f"shutting device down, offroad since {off_ts}")
+      # CLEARPILOT: signal dashcamd to close recording gracefully before power-off
+      params.put_bool("DashcamShutdown", True)
+      deadline = time.monotonic() + 15.0
+      while time.monotonic() < deadline:
+        if not params.getBool("DashcamShutdown"):
+          cloudlog.info("dashcamd shutdown ack received")
+          break
+        time.sleep(0.5)
+      else:
+        cloudlog.warning("dashcamd shutdown ack timeout, proceeding")
       params.put_bool("DoShutdown", True)
 
     msg.deviceState.started = started_ts is not None