feat: 4Hz fan control with gear/cruise-aware clamps; move hot signals to cereal

Fan control rework (thermald → 4Hz):
- DT_TRML 0.5s → 0.25s (thermald loop + fan PID now at 4Hz)
- New clamp rules based on (gear, cruise_engaged, standstill):
    parked                                → 0-100%
    in drive + cruise engaged (any speed) → 30-100%
    in drive + cruise off + standstill    → 10-100%
    in drive + cruise off + moving        → 30-100%
- thermald now reads gearShifter (via carState) and controlsState.enabled,
  passes them to fan_controller.update()
- Removed BENCH_MODE special case — new rules cover bench automatically
- Removed ignition-based branches — gear is the correct signal

System health overlay:
- Subscribed UI to peripheralState so we can read fanSpeedRpm
- Added FAN row: actual fan% (RPM / 65) to sit alongside LAG/DROP/TEMP/CPU/MEM.
  Shows the real fan output vs. what the PID is asking for.

Migrate hot signals from paramsMemory to cereal (frogpilotCarControl):
- Added latRequested @3 and noLatLaneChange @4 to FrogPilotCarControl schema
- controlsd sets FPCC.latRequested / FPCC.noLatLaneChange (send-on-change
  already gates the IPC)
- modeld reads from sm['frogpilotCarControl'] (added to its subscribers)
  instead of paramsMemory (saves ~20 file-read syscalls/sec)
- carcontroller reads from frogpilot_variables (set in-process by controlsd)
  instead of paramsMemory (saves ~100 file-read syscalls/sec in 100Hz path).
  Dropped carcontroller's now-unused Params instance and import.
- UI (ui.cc, onroad.cc) reads from sm['frogpilotCarControl'].noLatLaneChange
- Removed LatRequested and no_lat_lane_change param registrations + defaults

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

common/realtime.py

@@ -12,7 +12,7 @@ from openpilot.system.hardware import PC
 # time step for each process
 DT_CTRL = 0.01  # controlsd
 DT_MDL = 0.05  # model
-DT_TRML = 0.5  # thermald and manager
+DT_TRML = 0.25  # thermald and manager — 4 Hz
 DT_DMON = 0.05  # driver monitoring