New LED behavior (active-low, PC15=LED1, PC14=LED2):
Disarmed, IMU OK : LED1 solid ON + LED2 off
Armed : LED1 solid ON + LED2 solid ON
Tilt fault : LED1 blink 1Hz + LED2 blink 1Hz
IMU error : LED1 blink 1Hz + LED2 solid ON
Rule: solid = good, slow blink (~1Hz) = needs attention.
Removed the confusing fast-blink-at-5Hz-for-error and the
baro-flash-every-5s patterns.
status_update() signature changed: baro_ok → armed + tilt_fault
so the LED pattern can reflect arm state directly.
Closes#22.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>