fix(tests): Align test_notebook_search_attribute_error with actual behavior

Updates assertions in `test_notebook_search_attribute_error`
to correctly expect a "No matches found" message object when
a cell's `source` attribute raises an AttributeError and no
other search results are found.

The test previously expected an empty list, but the search
function's logic is to return a specific message in this scenario.

Author: jbeno

tests/test_tools_coverage_additional.py

@@ -448,7 +448,9 @@ async def test_notebook_search_attribute_error(notebook_tools, sample_notebook_p
 
     # The method should handle the error and continue
     assert isinstance(result, list)
-    assert len(result) == 0  # No matches found
+    assert len(result) == 1
+    assert "message" in result[0]
+    assert "No matches found" in result[0]["message"]
 
 @pytest.mark.asyncio
 async def test_notebook_search_cell_error(notebook_tools, sample_notebook_path):