feat(radio): honest TX power for GAT562 30S external PA

gat562_30s_mesh_kit has an always-on external PA rated at +30dBm, but the
firmware wrote tx_power_dbm straight to the SX1262 register (capped at 22),
so the app/CLI/UI never matched the real radiated power and couldn't ask
for more than 22 even though the hardware supports it.

Add a generic, macro-gated PA gain-curve resolution in
RadioLibWrapper::setTxPower() (the single choke point every TX-power path
already funnels through), reusable by any future board with a similar PA.
For this board, reuse the vendor-measured 869MHz curve from the open
upstream Meshtastic PR that added it for the same physical module
(meshtastic/firmware#11212): pick the lowest SX1262 setting whose measured
output reaches the requested dBm, clamped at the PA's saturation knee.
Bump LORA_TX_POWER/MAX_LORA_TX_POWER to 30 for this variant only -- the
other three GAT562 boards use the SX1262's own PA_BOOST (22dBm, no
external PA) and are unaffected.

Since a request below the PA's floor gain (14dBm) still radiates at that
floor, also make CommonCLICallbacks::setTxPower() return what was actually
applied, and have every setter (BLE CMD_SET_RADIO_TX_POWER, CLI "tx",
simple_repeater/room_server/sensor) persist and report that value instead
of the raw request -- so tx_power_dbm never silently disagrees with the
physical output in either direction.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

examples/companion_radio/MyMesh.cpp

@@ -2488,9 +2488,11 @@ void MyMesh::handleCmdFrame(size_t len) {
     if (power < -9 || power > MAX_LORA_TX_POWER) {
       writeErrFrame(ERR_CODE_ILLEGAL_ARG);
     } else {
-      _prefs.tx_power_dbm = power;
+      radio_driver.setTxPower(power);
+      // Store what the radio actually applied, not the raw request -- on a
+      // board with an external-PA gain curve those can differ (see setTxPower()).
+      _prefs.tx_power_dbm = radio_driver.getTxPower();
       savePrefs();
-      radio_driver.setTxPower(_prefs.tx_power_dbm);
       writeOKFrame();
     }
   } else if (cmd_frame[0] == CMD_SET_TUNING_PARAMS) {

examples/simple_repeater/MyMesh.cpp

@@ -1095,8 +1095,9 @@ void MyMesh::dumpLogFile() {
   }
 }
 
-void MyMesh::setTxPower(int8_t power_dbm) {
+int8_t MyMesh::setTxPower(int8_t power_dbm) {
   radio_driver.setTxPower(power_dbm);
+  return radio_driver.getTxPower();
 }
 
 bool MyMesh::setRxBoostedGain(bool enable) {

examples/simple_repeater/MyMesh.h

@@ -212,7 +212,7 @@ public:
   }
 
   void dumpLogFile() override;
-  void setTxPower(int8_t power_dbm) override;
+  int8_t setTxPower(int8_t power_dbm) override;
   void formatNeighborsReply(char *reply) override;
   void removeNeighbor(const uint8_t* pubkey, int key_len) override;
   void formatStatsReply(char *reply) override;

examples/simple_room_server/MyMesh.cpp

@@ -839,8 +839,9 @@ void MyMesh::dumpLogFile() {
   }
 }
 
-void MyMesh::setTxPower(int8_t power_dbm) {
+int8_t MyMesh::setTxPower(int8_t power_dbm) {
   radio_driver.setTxPower(power_dbm);
+  return radio_driver.getTxPower();
 }
 
 bool MyMesh::setRxBoostedGain(bool enable) {

examples/simple_room_server/MyMesh.h

@@ -208,7 +208,7 @@ public:
   }
 
   void dumpLogFile() override;
-  void setTxPower(int8_t power_dbm) override;
+  int8_t setTxPower(int8_t power_dbm) override;
   bool setRxBoostedGain(bool enable) override;
 
   void formatNeighborsReply(char *reply) override {

examples/simple_sensor/SensorMesh.cpp

@@ -848,8 +848,9 @@ void SensorMesh::updateFloodAdvertTimer() {
   }
 }
 
-void SensorMesh::setTxPower(int8_t power_dbm) {
+int8_t SensorMesh::setTxPower(int8_t power_dbm) {
   radio_driver.setTxPower(power_dbm);
+  return radio_driver.getTxPower();
 }
 
 void SensorMesh::formatStatsReply(char *reply) {

examples/simple_sensor/SensorMesh.h

@@ -67,7 +67,7 @@ public:
   void setLoggingOn(bool enable) override {  }
   void eraseLogFile() override { }
   void dumpLogFile() override { }
-  void setTxPower(int8_t power_dbm) override;
+  int8_t setTxPower(int8_t power_dbm) override;
   void formatNeighborsReply(char *reply) override {
     strcpy(reply, "not supported");
   }