refactor: simplify _get_service_pids — dedupe systemd scopes, fix self-import, harden launchd parsing

- Loop over user/system scope args instead of duplicating the systemd block
- Call get_launchd_label() directly instead of self-importing from hermes_cli.gateway
- Validate launchd output by checking parts[2] matches expected label (skip header)
- Add race-condition assumption docstring

tests/hermes_cli/test_update_gateway_restart.py

@@ -662,6 +662,7 @@ class TestGetServicePids:
     def test_returns_launchd_pid(self, monkeypatch):
         monkeypatch.setattr(gateway_cli, "is_linux", lambda: False)
         monkeypatch.setattr(gateway_cli, "is_macos", lambda: True)
+        monkeypatch.setattr(gateway_cli, "get_launchd_label", lambda: "ai.hermes.gateway")
 
         def fake_run(cmd, **kwargs):
             joined = " ".join(str(c) for c in cmd)