feat(tests): enable MCP tests in server mode

We would like to run all OpenAI compatibility tests using only the openai-client library. This is most friendly for contributors since they can run tests without needing to update the client-sdks (which is getting easier but still a long pole.)

This is the first step in enabling that -- no using "library client" for any of the Responses tests. This seems like a reasonable trade-off since the usage of an embeddeble library client for Responses (or any OpenAI-compatible) behavior seems to be not very common. To do this, we needed to enable MCP tests (which only worked in library client mode) for server mode.

tests/integration/responses/conftest.py

@@ -0,0 +1,17 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import pytest
+
+from llama_stack.core.library_client import LlamaStackAsLibraryClient
+
+
+@pytest.fixture
+def responses_client(compat_client):
+    """Provide a client for responses tests, skipping library client mode."""
+    if isinstance(compat_client, LlamaStackAsLibraryClient):
+        pytest.skip("Responses API tests are not supported in library client mode")
+    return compat_client