fix: report an invalid --port with a short message instead of listing every choice

tests/test_cli.py

@@ -33,3 +33,16 @@ def test_package_version_matches_pyproject() -> None:
 
     data = tomllib.loads((Path(__file__).parent.parent / "pyproject.toml").read_text())
     assert data["project"]["version"] == __version__
+
+
+@pytest.mark.parametrize("value", ["0", "65536", "-1", "http", "80.5"])
+def test_serve_rejects_bad_ports_with_a_short_message(
+    value: str, capsys: pytest.CaptureFixture[str]
+) -> None:
+    with pytest.raises(SystemExit) as exit_info:
+        build_parser().parse_args(["serve", "--port", value])
+
+    err = capsys.readouterr().err
+    assert exit_info.value.code == 2
+    assert "--port" in err and "65535" in err
+    assert len(err) < 500