Apply ruff 0.16 and black fixes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012U7coQfVu8nK2R4q2mCULA

tests/conftest.py

@@ -341,7 +341,7 @@ def serve_with_plugins(tmp_path):
         plugins_dir = tmp_path / "plugins"
         plugins_dir.mkdir(exist_ok=True)
         for module_name, source in plugins.items():
-            (plugins_dir / "{}.py".format(module_name)).write_text(source, "utf-8")
+            (plugins_dir / f"{module_name}.py").write_text(source, "utf-8")
         port = find_free_port()
         proc = subprocess.Popen(
             [
@@ -365,7 +365,7 @@ def serve_with_plugins(tmp_path):
         processes.append(proc)
         if wait_for_startup:
             wait_until_responds(
-                "http://127.0.0.1:{}/-/versions.json".format(port), process=proc
+                f"http://127.0.0.1:{port}/-/versions.json", process=proc
             )
         return proc, port
 

tests/test_cli_serve_server.py

@@ -145,6 +145,8 @@ def test_startup_error_fails_fast_before_port_binds(serve_with_plugins):
     # confirms the socket was not left bound; on its own it cannot prove the
     # failure preceded the bind, since a port nothing ever touched also
     # refuses connections.
-    with pytest.raises(OSError):
-        with socket.create_connection(("127.0.0.1", port), timeout=0.2):
-            pass
+    with (
+        pytest.raises(OSError),
+        socket.create_connection(("127.0.0.1", port), timeout=0.2),
+    ):
+        pass