fix: add auto-close to error HTML popup, strengthen spec_path registry test

- Error HTML page now auto-closes the popup after 4s (same as success
  page), stopping the 2s polling loop and clearing the loading spinner
  so users aren't left in a confused state after a provider error.
- Replace trivial `assert manager is not None` with a meaningful assertion:
  patch _create_mcp_client and verify it is NOT called for spec_path servers,
  directly testing the short-circuit in _get_tools_from_server.

litellm/proxy/_experimental/mcp_server/openapi_oauth2_endpoints.py

@@ -125,6 +125,10 @@ def _build_error_html(title: str, message: str) -> str:
   h2 {{ color: #dc2626; font-size: 20px; margin-bottom: 12px; }}
   p {{ color: #475569; font-size: 14px; line-height: 1.6; }}
 </style>
+<script>
+  // Auto-close error popup so the polling loop stops and the spinner clears
+  if (window.opener) {{ setTimeout(function() {{ window.close(); }}, 4000); }}
+</script>
 </head>
 <body>
 <div class="card">

tests/test_litellm/proxy/_experimental/mcp_server/test_openapi_oauth2_endpoints.py

@@ -585,8 +585,22 @@ def test_spec_path_server_uses_tool_registry():
 
     assert server.spec_path == "https://example.com/openapi.json"
     assert server.is_byok is True
-    # The spec_path short-circuit in _get_tools_from_server is conditional on this field
-    assert manager is not None
+
+    # Verify the manager's short-circuit path: _get_tools_from_server checks
+    # spec_path before attempting MCP client creation.  We confirm this by
+    # patching _create_mcp_client and asserting it is NOT called when spec_path is set.
+    from unittest.mock import AsyncMock, patch
+
+    with patch.object(manager, "_create_mcp_client", new_callable=AsyncMock) as mock_create:
+        # _get_tools_from_server is async but returns early for spec_path servers
+        import asyncio
+
+        async def _run():
+            return await manager._get_tools_from_server(server)
+
+        asyncio.get_event_loop().run_until_complete(_run())
+
+    mock_create.assert_not_called()
 
 
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