fix(gateway): bypass active-session guard for /approve and /deny commands (#4926)

The base adapter's active-session guard queues all messages when an agent
is running. This creates a deadlock for /approve and /deny: the agent
thread is blocked on threading.Event.wait() in tools/approval.py waiting
for resolve_gateway_approval(), but the /approve command is queued waiting
for the agent to finish.

Dispatch /approve and /deny directly to the message handler (which routes
to gateway/run.py's _handle_approve_command) without going through
_process_message_background — avoids spawning a competing background task
that would mess with session lifecycle/guards.

Fixes #4898
Co-authored-by: mechovation (original diagnosis in PR #4904)

gateway/platforms/base.py

@@ -1022,6 +1022,32 @@ class BasePlatformAdapter(ABC):
         
         # Check if there's already an active handler for this session
         if session_key in self._active_sessions:
+            # /approve and /deny must bypass the active-session guard.
+            # The agent thread is blocked on threading.Event.wait() inside
+            # tools/approval.py — queuing these commands creates a deadlock:
+            # the agent waits for approval, approval waits for agent to finish.
+            # Dispatch directly to the message handler without touching session
+            # lifecycle (no competing background task, no session guard removal).
+            cmd = event.get_command()
+            if cmd in ("approve", "deny"):
+                logger.debug(
+                    "[%s] Approval command '/%s' bypassing active-session guard for %s",
+                    self.name, cmd, session_key,
+                )
+                try:
+                    _thread_meta = {"thread_id": event.source.thread_id} if event.source.thread_id else None
+                    response = await self._message_handler(event)
+                    if response:
+                        await self._send_with_retry(
+                            chat_id=event.source.chat_id,
+                            content=response,
+                            reply_to=event.message_id,
+                            metadata=_thread_meta,
+                        )
+                except Exception as e:
+                    logger.error("[%s] Approval dispatch failed: %s", self.name, e, exc_info=True)
+                return
+
             # Special case: photo bursts/albums frequently arrive as multiple near-
             # simultaneous messages. Queue them without interrupting the active run,
             # then process them immediately after the current task finishes.