[esp32_ble] Fix EventPool/LockFreeQueue sizing off-by-one (#14892)

esphome/components/esp32_ble/ble.cpp

@@ -575,8 +575,9 @@ template<typename... Args> void enqueue_ble_event(Args... args) {
   load_ble_event(event, args...);
 
   // Push the event to the queue
+  // Push always succeeds: pool is sized to queue capacity (N-1), so if
+  // allocate() returned non-null, the queue is guaranteed to have room.
   global_ble->ble_events_.push(event);
-  // Push always succeeds because we're the only producer and the pool ensures we never exceed queue size
 }
 
 // Explicit template instantiations for the friend function

esphome/components/esp32_ble/ble.h

@@ -221,7 +221,13 @@ class ESP32BLE : public Component {
 
   // Large objects (size depends on template parameters, but typically aligned to 4 bytes)
   esphome::LockFreeQueue<BLEEvent, MAX_BLE_QUEUE_SIZE> ble_events_;
-  esphome::EventPool<BLEEvent, MAX_BLE_QUEUE_SIZE> ble_event_pool_;
+  // Pool sized to queue capacity (SIZE-1) because LockFreeQueue<T,N> is a ring
+  // buffer that holds N-1 elements (one slot distinguishes full from empty).
+  // This guarantees allocate() returns nullptr before push() can fail, which:
+  //  1. Prevents leaking a pool slot (the Nth allocate succeeds but push fails)
+  //  2. Avoids needing release() on the producer path after a failed push(),
+  //     preserving the SPSC contract on the pool's internal free list
+  esphome::EventPool<BLEEvent, MAX_BLE_QUEUE_SIZE - 1> ble_event_pool_;
 
   // 4-byte aligned members
 #ifdef USE_ESP32_BLE_ADVERTISING