fix(mqtt): count only failed starts, not rejected reconnects, in cf

reconnect() on a started client returns ESP_FAIL while an attempt is already
in progress. On a Heltec V3, a live reconfigure hit exactly that and the
attempt then connected, yet cf read 1. Count start_failures only when
connect() on a stopped client fails, and restore the attempt flag to its
prior value on any failed call so the in-progress attempt is still judged by
its own outcome.

src/helpers/bridges/MQTTBridge.cpp

@@ -2512,8 +2512,10 @@ esp_err_t MQTTBridge::reconnectSlotClient(int index) {
   }
 
   esp_err_t r;
+  const bool was_pending = _slot_attempt_pending[index];
+  const bool starting = !slot.client->isStarted();
   _slot_attempt_pending[index] = true;
-  if (!slot.client->isStarted()) {
+  if (starting) {
     MQTT_DEBUG_PRINTLN("MQTT%d start (client was stopped)", index + 1);
     r = slot.client->connect();
   } else {
@@ -2526,8 +2528,11 @@ esp_err_t MQTTBridge::reconnectSlotClient(int index) {
     // is the point at which a freshly minted token becomes the one in use.
     slot.applied_token_expires_at = slot.token_expires_at;
   } else {
-    _slot_attempt_pending[index] = false;
-    slot.start_failures++;
+    _slot_attempt_pending[index] = was_pending;
+    // A failed start (buffer/task allocation, config) means no attempt could begin.
+    // reconnect() on a started client returns ESP_FAIL while one is already in
+    // progress, which is not a failure (seen on hardware after a reconfigure).
+    if (starting) slot.start_failures++;
   }
   return r;
 }

src/helpers/bridges/MQTTBridge.h

@@ -187,9 +187,9 @@ private:
     // disconnect_count (which also counts dropped live sessions) and from the
     // publish error counter, which cannot move at all while a slot is down.
     uint32_t connect_failures;
-    // connect()/reconnect() calls that returned an error, so no attempt started and
-    // no event will arrive. Written only by the bridge task; reported summed with
-    // connect_failures.
+    // connect() calls on a stopped client that returned an error, so no attempt
+    // started and no event will arrive. Written only by the bridge task; reported
+    // summed with connect_failures.
     uint32_t start_failures;
     unsigned long first_disconnect_time; // millis() of first disconnect after boot