fix(gateway): drain manual profile gateways via SIGUSR1 before respawn

The PR wired in a detached watcher that respawns manual profile gateways
after they exit.  Pair that with a SIGUSR1 graceful drain (same path
systemd/launchd use) so in-flight agent runs finish instead of getting
SIGTERM'd.  Fall back to SIGTERM if SIGUSR1 isn't wired or the gateway
doesn't exit within the drain budget — the watcher sees the exit and
relaunches either way.

Tested end-to-end against an orphaned gateway: graceful drain exits in
0.5s and the watcher fires the relaunch command.

hermes_cli/main.py

@@ -7438,13 +7438,23 @@ def _cmd_update_impl(args, gateway_mode: bool):
                 if proc.pid in manual_pids
             }
             for pid, proc in profile_processes.items():
-                if launch_detached_profile_gateway_restart(proc.profile, pid):
+                if not launch_detached_profile_gateway_restart(proc.profile, pid):
+                    continue
+                # Prefer a graceful SIGUSR1 drain so in-flight agent runs
+                # finish before the watcher respawns the gateway.  If the
+                # gateway doesn't support SIGUSR1 or doesn't exit within
+                # the drain budget, fall back to SIGTERM — the watcher
+                # still sees the exit and relaunches either way.
+                drained = _graceful_restart_via_sigusr1(
+                    pid, drain_timeout=_drain_budget,
+                )
+                if not drained:
                     try:
                         os.kill(pid, _signal.SIGTERM)
-                        killed_pids.add(pid)
-                        relaunched_profiles.append(proc.profile)
                     except (ProcessLookupError, PermissionError):
                         pass
+                killed_pids.add(pid)
+                relaunched_profiles.append(proc.profile)
 
             for pid in manual_pids:
                 if pid in profile_processes:

tests/hermes_cli/test_update_gateway_restart.py

@@ -418,15 +418,55 @@ class TestCmdUpdateLaunchdRestart:
         with patch.object(gateway_cli, "find_gateway_pids", return_value=[12345]), \
              patch.object(gateway_cli, "find_profile_gateway_processes", return_value=[process]), \
              patch.object(gateway_cli, "launch_detached_profile_gateway_restart", return_value=True) as restart, \
+             patch.object(gateway_cli, "_graceful_restart_via_sigusr1", return_value=True) as graceful, \
              patch("os.kill") as kill:
             cmd_update(mock_args)
 
         captured = capsys.readouterr().out
         restart.assert_called_once_with("coder", 12345)
-        kill.assert_called_once()
+        graceful.assert_called_once()
+        # Graceful drain succeeded — no SIGTERM fallback needed.
+        kill.assert_not_called()
         assert "Restarting manual gateway profile(s): coder" in captured
         assert "Restart manually: hermes gateway run" not in captured
 
+    @patch("shutil.which", return_value=None)
+    @patch("subprocess.run")
+    def test_update_profile_manual_gateway_falls_back_to_sigterm(
+        self, mock_run, _mock_which, mock_args, capsys, tmp_path, monkeypatch,
+    ):
+        """When graceful SIGUSR1 drain fails, manual profile restart falls back to SIGTERM."""
+        monkeypatch.setattr(gateway_cli, "is_macos", lambda: True)
+        monkeypatch.setattr(
+            gateway_cli,
+            "get_launchd_plist_path",
+            lambda: tmp_path / "ai.hermes.gateway.plist",
+        )
+
+        mock_run.side_effect = _make_run_side_effect(
+            commit_count="3",
+            launchctl_loaded=False,
+        )
+        process = gateway_cli.ProfileGatewayProcess(
+            profile="coder",
+            path=tmp_path / ".hermes" / "profiles" / "coder",
+            pid=12345,
+        )
+
+        with patch.object(gateway_cli, "find_gateway_pids", return_value=[12345]), \
+             patch.object(gateway_cli, "find_profile_gateway_processes", return_value=[process]), \
+             patch.object(gateway_cli, "launch_detached_profile_gateway_restart", return_value=True) as restart, \
+             patch.object(gateway_cli, "_graceful_restart_via_sigusr1", return_value=False) as graceful, \
+             patch("os.kill") as kill:
+            cmd_update(mock_args)
+
+        captured = capsys.readouterr().out
+        restart.assert_called_once_with("coder", 12345)
+        graceful.assert_called_once()
+        # Graceful drain returned False → SIGTERM fallback.
+        kill.assert_called_once()
+        assert "Restarting manual gateway profile(s): coder" in captured
+
     @patch("shutil.which", return_value=None)
     @patch("subprocess.run")
     def test_update_with_systemd_still_restarts_via_systemd(