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>

src/helpers/CommonCLI.cpp

@@ -706,9 +706,10 @@ void CommonCLI::handleSetCmd(uint32_t sender_timestamp, char* command, char* rep
       strcpy(reply, "OK");
     }
   } else if (memcmp(config, "tx ", 3) == 0) {
-    _prefs->tx_power_dbm = atoi(&config[3]);
+    // 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 = _callbacks->setTxPower(atoi(&config[3]));
     savePrefs();
-    _callbacks->setTxPower(_prefs->tx_power_dbm);
     strcpy(reply, "OK");
   } else if (sender_timestamp == 0 && memcmp(config, "freq ", 5) == 0) {
     _prefs->freq = atof(&config[5]);

src/helpers/CommonCLI.h

@@ -207,7 +207,11 @@ public:
   virtual void setLoggingOn(bool enable) = 0;
   virtual void eraseLogFile() = 0;
   virtual void dumpLogFile() = 0;
-  virtual void setTxPower(int8_t power_dbm) = 0;
+  // Returns the dBm the radio actually applied -- on a board with an
+  // external-PA gain curve this can differ from power_dbm (e.g. a request
+  // below the PA's floor gain still radiates at that floor), so callers
+  // should persist/report the return value, not the raw request.
+  virtual int8_t setTxPower(int8_t power_dbm) = 0;
   virtual void formatNeighborsReply(char *reply) = 0;
   virtual void removeNeighbor(const uint8_t* pubkey, int key_len) {
     // no op by default

src/helpers/radiolib/CustomSX1262Wrapper.h

@@ -97,7 +97,7 @@ public:
       ((CustomSX1262 *)_radio)->setCodingRate(_wd_cr);
       updatePreamble(_wd_sf);
     }
-    _radio->setOutputPower(getTxPower());
+    setTxPower(getTxPower());   // re-run through the wrapper's own setter so any PA gain curve reapplies
     // Unconditional: std_init() may have just turned boosted gain back ON via
     // the board's SX126X_RX_BOOSTED_GAIN compile default, so the OFF case
     // needs reapplying just as much as ON.

src/helpers/radiolib/RadioLibWrappers.cpp

@@ -52,8 +52,23 @@ uint32_t RadioLibWrapper::getRngSeed() {
 }
 
 void RadioLibWrapper::setTxPower(int8_t dbm) {
-  _tx_dbm = dbm;
+  _tx_dbm = dbm;   // logical/requested power -- what getTxPower(), the app and the CLI report
+#if defined(NUM_PA_POINTS) && defined(TX_GAIN_LORA)
+  // Per-board external-PA gain curve (radio_dbm -> measured gain in dB, from
+  // the vendor/GAT562-30S data cited in the upstream Meshtastic PR that added
+  // it, meshtastic/firmware#11212). The PA is always-on (no enable pin), so
+  // the SX1262 register alone decides real output; pick the lowest register
+  // setting whose (setting + its measured gain) reaches the requested dBm,
+  // clamping to the last entry once the PA saturates.
+  static const int8_t pa_gain[NUM_PA_POINTS] = { TX_GAIN_LORA };
+  int8_t radio_dbm = NUM_PA_POINTS - 1;
+  for (int i = 0; i < NUM_PA_POINTS; i++) {
+    if ((i + pa_gain[i]) >= dbm) { radio_dbm = i; break; }
+  }
+  _radio->setOutputPower(radio_dbm);
+#else
   _radio->setOutputPower(dbm);
+#endif
 }
 
 void RadioLibWrapper::idle() {