ArduPilot sensor libraries (AP_InertialSensor, AP_GPS, AP_Compass, AP_Baro, RangeFinder,
AP_Airspeed, AP_OpticalFlow, AP_BattMonitor, AP_Proximity, AP_AHRS, and more). Use when:
(1) Reading sensor data in ArduPilot code
(2) Adding new sensor drivers or backends
(3) Understanding frontend/backend architecture
(4) Debugging sensor health, calibration, or data flow
(5) Working with peripheral sensors (ESC telemetry, RPM, temperature, etc.)