fix(windows): probe compute host liveness without sending signals

tui_gateway/host_supervisor.py

@@ -22,6 +22,8 @@ from collections.abc import Callable
 from pathlib import Path
 from typing import Any
 
+import psutil
+
 from hermes_constants import get_hermes_home
 from tools.environments.local import hermes_subprocess_env
 
@@ -112,17 +114,9 @@ def _default_registry_path() -> Path:
 
 
 def _pid_alive(pid: int) -> bool:
-    if pid <= 0:
-        return False
-    try:
-        os.kill(pid, 0)
-        return True
-    except ProcessLookupError:
-        return False
-    except PermissionError:
-        return True
-    except Exception:
-        return False
+    # Signal zero is not a portable liveness query (CTRL_C_EVENT on Windows).
+    # pid_exists also distinguishes exited Windows processes with open handles.
+    return pid > 0 and psutil.pid_exists(pid)
 
 
 def _pid_command(pid: int) -> str: