test(cli): split the incomplete-fleet-restart hint tests per host

Once the launchd file carried the macos_only marker, the first real macOS
lane run showed TestIncompleteWarningMentionsLaunchctl asserting the
systemd-host branch (kickstart hint, systemctl line) that never runs on
macOS. The two Linux-arm tests move to their own linux_only file; the
launchd file keeps the macOS arm (bootstrap/list hint, no systemctl).

tests/hermes_cli/test_update_fleet_incomplete_warning.py

@@ -0,0 +1,27 @@
+"""Incomplete-fleet-restart hint on a systemd host (Linux arm of
+``_warn_incomplete_gateway_fleet_restart``; the macOS arm lives in
+test_update_launchd_fleet_restart.py). Regression for #111866: this class used to
+sit in the launchd file, where it asserted the non-macOS branch under a faked
+``is_macos()`` — green on Linux, never run on macOS, wrong on both."""
+
+from __future__ import annotations
+
+import pytest
+
+from hermes_cli.update_cmd_fleet import _warn_incomplete_gateway_fleet_restart
+
+pytestmark = pytest.mark.linux_only
+
+
+def test_launchd_labels_get_launchctl_hint(capsys):
+    _warn_incomplete_gateway_fleet_restart(["ai.hermes.gateway-merit-ops"])
+    out = capsys.readouterr().out
+    assert "Update incomplete" in out
+    assert "launchctl kickstart -k" in out
+
+
+def test_systemd_units_keep_systemctl_hint(capsys):
+    _warn_incomplete_gateway_fleet_restart(["hermes-gateway-coder"])
+    out = capsys.readouterr().out
+    assert "systemctl" in out
+    assert "launchctl" not in out

tests/hermes_cli/test_update_launchd_fleet_restart.py

@@ -640,15 +640,13 @@ class TestWaitForLaunchdServicePid:
         )
 
 
-class TestIncompleteWarningMentionsLaunchctl:
-    def test_launchd_labels_get_launchctl_hint(self, capsys):
+class TestIncompleteWarningOnMacos:
+    """On the launchd host the hint is bootstrap/list, never the systemd or the
+    ``kickstart`` line — a label in this list is likely deregistered (#88848)."""
+
+    def test_launchd_labels_get_bootstrap_hint(self, capsys):
         _warn_incomplete_gateway_fleet_restart(["ai.hermes.gateway-merit-ops"])
         out = capsys.readouterr().out
         assert "Update incomplete" in out
-        assert "launchctl kickstart -k" in out
-
-    def test_systemd_units_keep_systemctl_hint(self, capsys):
-        _warn_incomplete_gateway_fleet_restart(["hermes-gateway-coder"])
-        out = capsys.readouterr().out
-        assert "systemctl" in out
-        assert "launchctl" not in out
+        assert "launchctl bootstrap" in out
+        assert "systemctl" not in out