radio: extract CadController and NoiseFloorEstimator, one prefs source

- CadController (stats, window, re-anchor, visits, staircase, safety,
  starvation relax) and NoiseFloorEstimator split out of LoRaRadioBase
  behind a 4-call CadHw interface; Zephyr-free, host unit tests added
- prefs mandatory: setPrefs() before begin(), LoRaConfig fallbacks and the
  companion/observer placeholder prefs removed; LoRaConfig is the one
  defaults source (invalid-prefs fallback now uses the board TX default)
- TX-wait thread stack owned by the base; reconfigureWithParams removed
- driver extension headers on the public include path
  (zephyr/drivers/lora/*.h); patch 0003 include updated
- comment diet (image-identical); rationale moved to devdocs LLD 03

zephcore/app/RoomServerMesh.cpp

@@ -816,12 +816,6 @@ void RoomServerMesh::begin(RepeaterDataStore* store) {
 		}
 	}
 
-	/* NOTE: Radio configuration is handled by SX126xRadio adapter using
-	 * LoRaConfig defaults. The room server uses the same radio params as companion.
-	 * Dynamic radio reconfiguration (via CLI) is not yet supported - radio
-	 * uses compile-time defaults from LoRaConfig. This avoids EBUSY errors
-	 * from trying to reconfigure while radio is in async RX mode. */
-
 	updateAdvertTimer();
 	updateFloodAdvertTimer();