Fix command registry leaking between tests

tests/test_commands.py

@@ -12,6 +12,15 @@ from mudlib.render.ansi import RESET
 from mudlib.zone import Zone
 
 
+@pytest.fixture(autouse=True)
+def _clean_test_commands():
+    """Snapshot and restore command registry to prevent test leakage."""
+    snapshot = dict(commands._registry)
+    yield
+    commands._registry.clear()
+    commands._registry.update(snapshot)
+
+
 @pytest.fixture
 def mock_writer():
     writer = MagicMock()