fix(webui): clear stuck streaming after reconnect and improve stop reliability

After a gateway restart or websocket reconnect, the UI stays stuck in
processing state because reconnecting clients only replay running status
when a turn is active, never push idle when no turn is running.

Fix _hydrate_after_subscribe to always push goal_status (running with
started_at when turn is active, idle when no turn is running) so the
frontend can reset its processing indicator on reconnect.

Also fix cmd_stop reporting 'No active task to stop' when a task is
actually processing by draining the pending injection queue in addition
to cancelling active tasks. This prevents mid-turn injection deadlocks
and gives accurate task counts.

nanobot/channels/websocket.py

@@ -346,7 +346,11 @@ class WebSocketChannel(BaseChannel):
     async def _hydrate_after_subscribe(self, chat_id: str) -> None:
         """Replay goal/run strip state after subscribe (same-process refresh)."""
         await self._maybe_push_active_goal_state(chat_id)
-        await self._maybe_push_turn_run_wall_clock(chat_id)
+        t0 = websocket_turn_wall_started_at(chat_id)
+        if t0 is not None:
+            await self.send_goal_status(chat_id, "running", started_at=t0)
+        else:
+            await self.send_goal_status(chat_id, "idle")
 
     async def _send_event(self, connection: Any, event: str, **fields: Any) -> None:
         """Send a control event (attached, error, ...) to a single connection."""