fix(gateway): handle Windows stop fallback

nanobot/gateway/runtime.py

@@ -293,14 +293,26 @@ class GatewayRuntime:
     def _terminate_windows(self, pid: int, *, timeout_s: int) -> bool:
         ctrl_break = getattr(signal, "CTRL_BREAK_EVENT", None)
         if ctrl_break is not None:
-            with suppress(ProcessLookupError):
+            # Detached Windows children can reject CTRL_BREAK_EVENT with WinError 87;
+            # keep the existing taskkill fallback for that process shape.
+            with suppress(ProcessLookupError, OSError):
                 os.kill(pid, ctrl_break)
             if self._wait_for_exit(pid, timeout_s):
                 return True
-        self._subprocess_run(["taskkill", "/PID", str(pid), "/T"], check=False)
+        self._subprocess_run(
+            ["taskkill", "/PID", str(pid), "/T"],
+            check=False,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
         if self._wait_for_exit(pid, 2):
             return True
-        self._subprocess_run(["taskkill", "/PID", str(pid), "/T", "/F"], check=False)
+        self._subprocess_run(
+            ["taskkill", "/PID", str(pid), "/T", "/F"],
+            check=False,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
         return self._wait_for_exit(pid, 2)
 
     def _wait_for_exit(self, pid: int, timeout_s: int | float) -> bool: