fix: restore agent.close() cleanup and correct /restart category

- Add agent.close() call to _finalize_shutdown_agents() to prevent
  zombie processes (terminal sandboxes, browser daemons, httpx clients)
- Global cleanup (process_registry, environments, browsers) preserved
  in _stop_impl() during conflict resolution
- Move /restart CommandDef from 'Info' to 'Session' category to match
  /stop and /status

gateway/run.py

@@ -1275,6 +1275,14 @@ class GatewayRunner:
                     agent.shutdown_memory_provider()
             except Exception:
                 pass
+            # Close tool resources (terminal sandboxes, browser daemons,
+            # background processes, httpx clients) to prevent zombie
+            # process accumulation.
+            try:
+                if hasattr(agent, 'close'):
+                    agent.close()
+            except Exception:
+                pass
 
     async def _launch_detached_restart_command(self) -> None:
         import shutil