test: code quality fixes — docstring count, ruff format, test name accuracy

- Update test_tls.py module docstring: '9 tests' → '12 tests' (stale after edge case additions)
- Parenthesize assertion message on line 177 of test_tls.py (ruff line-length format)
- Rename test_serve_warns_when_only_cert_set → test_serve_no_ssl_when_only_cert_set
  to accurately reflect test behavior (verifies no SSL, not that a warning is printed)

muxplex/tests/test_cli.py

@@ -1641,7 +1641,7 @@ def test_doctor_shows_tls_clipboard_warning(tmp_path, monkeypatch, capsys):
 # ---------------------------------------------------------------------------
 
 
-def test_serve_warns_when_only_cert_set(tmp_path, monkeypatch, capsys):
+def test_serve_no_ssl_when_only_cert_set(tmp_path, monkeypatch, capsys):
     """serve() must NOT enable SSL when tls_cert is set but tls_key is empty string."""
     import muxplex.cli as cli_mod
 

muxplex/tests/test_tls.py

@@ -1,6 +1,6 @@
 """
 Tests for muxplex/tls.py — TLS certificate generation and inspection.
-9 tests covering generate_self_signed() and get_cert_info().
+12 tests covering generate_self_signed() and get_cert_info().
 """
 
 import stat
@@ -174,7 +174,9 @@ def test_generate_self_signed_with_custom_hostnames(tmp_path):
     result = generate_self_signed(cert_path, key_path, hostnames=custom_hostnames)
 
     assert isinstance(result, dict), "generate_self_signed() must return a dict"
-    assert isinstance(result.get("hostnames"), list), "result['hostnames'] must be a list"
+    assert isinstance(result.get("hostnames"), list), (
+        "result['hostnames'] must be a list"
+    )
     assert "mybox.local" in result["hostnames"], (
         f"'mybox.local' must be in result['hostnames'], got: {result['hostnames']!r}"
     )