fix(gateway): defer background review notifications until after main reply

Background review notifications ("💾 Skill created", "💾 Memory updated")
could race ahead of the main assistant reply in chat, making it look like
the agent stopped after creating a skill.

Gate bg-review notifications behind a threading.Event + pending queue.
Register a release callback on the adapter's _post_delivery_callbacks dict
so base.py's finally block fires it after the main response is delivered.

The queued-message path in _run_agent pops and calls the callback directly
to prevent double-fire.

Co-authored-by: Hermes Agent <hermes@nousresearch.com>
Closes #10541

gateway/platforms/base.py

@@ -839,6 +839,11 @@ class BasePlatformAdapter(ABC):
         # Gateway shutdown cancels these so an old gateway instance doesn't keep
         # working on a task after --replace or manual restarts.
         self._background_tasks: set[asyncio.Task] = set()
+        # One-shot callbacks to fire after the main response is delivered.
+        # Keyed by session_key.  GatewayRunner uses this to defer
+        # background-review notifications ("💾 Skill created") until the
+        # primary reply has been sent.
+        self._post_delivery_callbacks: Dict[str, Callable] = {}
         self._expected_cancelled_tasks: set[asyncio.Task] = set()
         self._busy_session_handler: Optional[Callable[[MessageEvent, str], Awaitable[bool]]] = None
         # Chats where auto-TTS on voice input is disabled (set by /voice off)
@@ -1894,6 +1899,14 @@ class BasePlatformAdapter(ABC):
             except Exception:
                 pass  # Last resort — don't let error reporting crash the handler
         finally:
+            # Fire any one-shot post-delivery callback registered for this
+            # session (e.g. deferred background-review notifications).
+            _post_cb = getattr(self, "_post_delivery_callbacks", {}).pop(session_key, None)
+            if callable(_post_cb):
+                try:
+                    _post_cb()
+                except Exception:
+                    pass
             # Stop typing indicator
             typing_task.cancel()
             try: