chore: import upstream snapshot with attribution

tests/server/test_fastapi_app.py

@@ -0,0 +1,24 @@
+import pytest
+from starlette.testclient import TestClient
+from starlette.websockets import WebSocketDisconnect
+
+from mlflow.server.fastapi_app import create_fastapi_app
+
+
+@pytest.fixture
+def client():
+    return TestClient(create_fastapi_app())
+
+
+def test_websocket_to_wsgi_mount_does_not_crash(client):
+    # A WebSocket handshake routed to the catch-all WSGI mount must be rejected
+    # cleanly (close code 1000) instead of raising AssertionError.
+    with pytest.raises(WebSocketDisconnect) as excinfo:  # noqa: PT011
+        with client.websocket_connect("/gateway/proxy/codex/v1/models"):
+            pass
+    assert excinfo.value.code == 1000
+
+
+def test_http_to_wsgi_mount_still_served(client):
+    resp = client.get("/health")
+    assert resp.status_code == 200