feat: update doctor() to show serve config and fix service install message

- Add serve config display in doctor() showing host, port, auth, and
  session_ttl from settings.json (inserted after Settings file block)
- Update two 'not installed' messages from 'muxplex install-service'
  to 'muxplex service install' (macOS launchd and Linux systemd sections)
- Add test_doctor_shows_serve_config verifying custom settings values
  (0.0.0.0, 9999, password) appear in doctor() output

muxplex/cli.py

@@ -264,6 +264,15 @@ def doctor() -> None:
             f"  {warn_mark} Settings: {SETTINGS_PATH} (not yet created — will use defaults)"
         )
 
+    # Serve config
+    from muxplex.settings import load_settings  # noqa: PLC0415
+
+    cfg = load_settings()
+    print(
+        f"  {ok_mark} Serve config: {cfg['host']}:{cfg['port']}"
+        f" (auth={cfg['auth']}, ttl={cfg['session_ttl']}s)"
+    )
+
     # Auth status
     pw_path = get_password_path()
     if pam_available():
@@ -314,7 +323,7 @@ def doctor() -> None:
                 )
         else:
             print(
-                f"  {warn_mark} Service: not installed (run: muxplex install-service)"
+                f"  {warn_mark} Service: not installed (run: muxplex service install)"
             )
     else:
         systemd_user = Path.home() / ".config" / "systemd" / "user" / "muxplex.service"
@@ -326,7 +335,7 @@ def doctor() -> None:
             )
         else:
             print(
-                f"  {warn_mark} Service: not installed (run: muxplex install-service)"
+                f"  {warn_mark} Service: not installed (run: muxplex service install)"
             )
 
     print()  # trailing newline

muxplex/tests/test_cli.py

@@ -1003,3 +1003,25 @@ def test_help_shows_single_upgrade_line():
         "upgrade and update must appear as alias notation 'upgrade (update)', not two separate entries. "
         f"Got help text:\n{help_text}"
     )
+
+
+def test_doctor_shows_serve_config(tmp_path, monkeypatch, capsys):
+    """doctor() must show the current serve config (host, port, auth)."""
+    import json
+
+    import muxplex.settings as settings_mod
+
+    settings_file = tmp_path / "settings.json"
+    settings_file.write_text(
+        json.dumps({"host": "0.0.0.0", "port": 9999, "auth": "password"})
+    )
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", settings_file)
+
+    from muxplex.cli import doctor
+
+    doctor()
+
+    out = capsys.readouterr().out
+    assert "0.0.0.0" in out
+    assert "9999" in out
+    assert "password" in out