fix(axelera): overload submits degrade to zero-rows, not raise

When the input queue is full, drop the frame's INFERENCE but keep the
1 submission : 1 result contract of AsyncDetectorRunner by emitting an
empty (20, 6) result for that connection_id (same pattern the producer
already uses when the buffer pool is starved). Raising here used to let a
burst of offered frames kill the detect worker and force a restart.
Test flipped: queue-full now asserts the zero-row drop instead of the raise.

frigate/detectors/plugins/axelera.py

@@ -424,13 +424,23 @@ class _AxeleraRuntimeInference:
     # -- public contract used by AxeleraDetector --------------------------
 
     def submit(self, connection_id: str, frame: np.ndarray) -> None:
-        """Queue one frame for inference, owned by `connection_id`."""
+        """Queue one frame for inference, owned by `connection_id`.
+
+        On overload (input queue full) the frame's INFERENCE is dropped but a
+        zero-row result is still emitted for `connection_id`: the async runner
+        contract is strictly 1 submission : 1 result (SHM cleanup + timing
+        pairing), so raising here would leave the runner waiting for a result
+        that never arrives.
+        """
         try:
             self._frame_q.put_nowait((connection_id, frame))
         except queue.Full:
-            raise RuntimeError(
-                "Axelera inference queue is full; restart required."
-            ) from None
+            logger.warning(
+                "axelera: inference queue full; dropping frame for %s",
+                connection_id,
+            )
+            self._push_result(connection_id, np.zeros((MAX_ROWS, 6), np.float32))
+            return
         self._ensure_threads()
 
     def _ensure_threads(self) -> None: