fix(mcp): Remove unsupported thumbnail/preview URLs and internal fields from MCP schemas (#38109)

tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py

@@ -258,7 +258,6 @@ class TestGetChartPreview:
         # Additional fields that may be present for backward compatibility
         _ = [
             "format",
-            "preview_url",
             "ascii_chart",
             "table_data",
             "width",

tests/unit_tests/mcp_service/chart/tool/test_list_charts.py

@@ -201,12 +201,12 @@ class TestChartDefaultColumnFiltering:
     def test_explicit_select_columns(self):
         """Test that explicit select_columns can include non-default columns."""
         request = ListChartsRequest(
-            select_columns=["id", "slice_name", "description", "form_data"]
+            select_columns=["id", "slice_name", "description", "cache_timeout"]
         )
         # Verify exact columns are present - explicit request should match exactly
         assert set(request.select_columns) == {
             "id",
             "slice_name",
             "description",
-            "form_data",
+            "cache_timeout",
         }