- Trigger noise floor calibration every 2s and AGC reset every 30s in main loop.
- Reorder loop to match Dispatcher: calibrate + radio.loop() before AGC reset
and recvRaw() so RSSI is never sampled right after startReceive().
- Update protocol doc with calibration intervals and typical noise floor range.
- Variant platformio.ini updates (heltec_v3, rak4631).