Extends #19994 to the restart path. Dashboard spawns 'hermes gateway restart' in the background; when a wedged adapter websocket pushes drain past the 90s CLI timeout, the dashboard previously surfaced a raw subprocess.TimeoutExpired traceback. Mirror systemd_stop()'s TimeoutExpired catch onto both forcing-restart sites in systemd_restart(). Adds a test that exercises the no-active-pid branch end-to-end.