feat: add stats-extpower CLI command for INA3221 power monitoring

Add a serial-only `stats-extpower` command that returns per-channel
voltage and current readings from the INA3221 external power monitoring
board as JSON. Returns an error message if no supported hardware is
detected.

Changes:
- New stats-extpower CLI command in CommonCLI.cpp
- formatExtPowerStatsReply virtual method added through the callback
  chain (CommonCLI.h → MyMesh)
- formatExtPowerStats implementation in EnvironmentSensorManager that
  reads INA3221 channels
- CLI documentation update

docs/cli_commands.md

@@ -127,6 +127,17 @@
 
 ---
 
+### External Power Monitoring Stats - Per-channel voltage and current
+**Usage:** `stats-extpower`
+
+**Serial Only:** Yes
+
+**Note:** Returns JSON with only enabled channels, e.g. `{"ch1_voltage_mv":12450,"ch1_current_ma":150,"ch2_voltage_mv":3800,"ch2_current_ma":85}`
+
+**Note:** Returns "No external power monitoring board detected" if no supported hardware is present
+
+---
+
 ## Logging
 
 ### Begin capture of rx log to node storage

examples/simple_repeater/MyMesh.cpp

@@ -1015,10 +1015,16 @@ void MyMesh::formatRadioStatsReply(char *reply) {
 }
 
 void MyMesh::formatPacketStatsReply(char *reply) {
-  StatsFormatHelper::formatPacketStats(reply, radio_driver, getNumSentFlood(), getNumSentDirect(), 
+  StatsFormatHelper::formatPacketStats(reply, radio_driver, getNumSentFlood(), getNumSentDirect(),
                                        getNumRecvFlood(), getNumRecvDirect());
 }
 
+void MyMesh::formatExtPowerStatsReply(char *reply) {
+  if (!sensors.formatExtPowerStats(reply)) {
+    strcpy(reply, "No external power monitoring board detected");
+  }
+}
+
 void MyMesh::saveIdentity(const mesh::LocalIdentity &new_id) {
 #if defined(NRF52_PLATFORM) || defined(STM32_PLATFORM)
   IdentityStore store(*_fs, "");

examples/simple_repeater/MyMesh.h

@@ -207,6 +207,7 @@ public:
   void formatStatsReply(char *reply) override;
   void formatRadioStatsReply(char *reply) override;
   void formatPacketStatsReply(char *reply) override;
+  void formatExtPowerStatsReply(char *reply) override;
 
   mesh::LocalIdentity& getSelfId() override { return self_id; }
 

src/helpers/CommonCLI.cpp

@@ -789,6 +789,8 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, const char* command, ch
       _callbacks->formatRadioStatsReply(reply);
     } else if (sender_timestamp == 0 && memcmp(command, "stats-core", 10) == 0 && (command[10] == 0 || command[10] == ' ')) {
       _callbacks->formatStatsReply(reply);
+    } else if (sender_timestamp == 0 && memcmp(command, "stats-extpower", 14) == 0 && (command[14] == 0 || command[14] == ' ')) {
+      _callbacks->formatExtPowerStatsReply(reply);
     } else {
       strcpy(reply, "Unknown command");
     }

src/helpers/CommonCLI.h

@@ -75,6 +75,9 @@ public:
   virtual void formatStatsReply(char *reply) = 0;
   virtual void formatRadioStatsReply(char *reply) = 0;
   virtual void formatPacketStatsReply(char *reply) = 0;
+  virtual void formatExtPowerStatsReply(char *reply) {
+    strcpy(reply, "No external power monitoring board detected");
+  };
   virtual mesh::LocalIdentity& getSelfId() = 0;
   virtual void saveIdentity(const mesh::LocalIdentity& new_id) = 0;
   virtual void clearStats() = 0;

src/helpers/SensorManager.h

@@ -23,6 +23,7 @@ public:
   virtual const char* getSettingValue(int i) const { return NULL; }
   virtual bool setSettingValue(const char* name, const char* value) { return false; }
   virtual LocationProvider* getLocationProvider() { return NULL; }
+  virtual bool formatExtPowerStats(char* reply) { return false; }
 
   // Helper functions to manage setting by keys (useful in many places ...)
   const char* getSettingByKey(const char* key) {

src/helpers/sensors/EnvironmentSensorManager.cpp

@@ -489,6 +489,31 @@ bool EnvironmentSensorManager::querySensors(uint8_t requester_permissions, Cayen
 }
 
 
+bool EnvironmentSensorManager::formatExtPowerStats(char* reply) {
+#if ENV_INCLUDE_INA3221
+  if (!INA3221_initialized) return false;
+  char* dp = reply;
+  *dp++ = '{';
+  bool first = true;
+  for (int i = 0; i < TELEM_INA3221_NUM_CHANNELS; i++) {
+    if (INA3221.isChannelEnabled(i)) {
+      int ch = i + 1;
+      int voltage_mv = (int)(INA3221.getBusVoltage(i) * 1000);
+      int current_ma = (int)(INA3221.getCurrentAmps(i) * 1000);
+      if (!first) *dp++ = ',';
+      sprintf(dp, "\"ch%d_voltage_mv\":%d,\"ch%d_current_ma\":%d", ch, voltage_mv, ch, current_ma);
+      dp = strchr(dp, 0);
+      first = false;
+    }
+  }
+  *dp++ = '}';
+  *dp = 0;
+  return true;
+#else
+  return false;
+#endif
+}
+
 int EnvironmentSensorManager::getNumSettings() const {
   int settings = 0;
   #if ENV_INCLUDE_GPS

src/helpers/sensors/EnvironmentSensorManager.h

@@ -55,4 +55,5 @@ public:
   const char* getSettingName(int i) const override;
   const char* getSettingValue(int i) const override;
   bool setSettingValue(const char* name, const char* value) override;
+  bool formatExtPowerStats(char* reply) override;
 };