fix(mcp): resolve ruff E501 and formatting issues to pass pre-commit

- Split long string literal in schema_validator.py line 202 (E501, 94 > 88 chars)
- Apply ruff format auto-fixes to big_number.py, handlebars.py, and test_get_chart_data.py

superset/mcp_service/chart/plugins/big_number.py

@@ -71,8 +71,7 @@ class BigNumberChartPlugin(BaseChartPlugin):
                 error_type="invalid_metric_type",
                 message="Big Number metric must be a dict with 'name' and 'aggregate'",
                 details=(
-                    "The 'metric' field must be an object, got "
-                    f"{type(metric).__name__}"
+                    f"The 'metric' field must be an object, got {type(metric).__name__}"
                 ),
                 suggestions=[
                     "Use a dict: {'name': 'col', 'aggregate': 'SUM'}",

superset/mcp_service/chart/plugins/handlebars.py

@@ -73,8 +73,7 @@ class HandlebarsChartPlugin(BaseChartPlugin):
                 ),
                 suggestions=[
                     "Ensure handlebars_template is a non-empty string",
-                    "Example: '<ul>{{#each data}}<li>{{this.name}}</li>"
-                    "{{/each}}</ul>'",
+                    "Example: '<ul>{{#each data}}<li>{{this.name}}</li>{{/each}}</ul>'",
                 ],
                 error_code="INVALID_HANDLEBARS_TEMPLATE",
             )

superset/mcp_service/chart/validation/schema_validator.py

@@ -199,7 +199,8 @@ class SchemaValidator:
             "details": "The XY chart configuration is missing required "
             "fields or has invalid structure",
             "suggestions": [
-                "Note: 'x' is optional and defaults to the dataset's primary datetime column",
+                "Note: 'x' is optional and defaults to the dataset's primary "
+                "datetime column",
                 "Ensure 'y' is an array: [{'name': 'metric', 'aggregate': 'SUM'}]",
                 "Check that all column names are strings",
                 "Verify aggregate functions are valid: SUM, COUNT, AVG, MIN, MAX",

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

@@ -222,9 +222,9 @@ class TestBigNumberChartFallback:
                 "viz_type": viz_type,
             }
             metrics, _ = _extract_metrics_and_groupby(form_data)
-            assert metrics == [
-                {"label": "plural_metric"}
-            ], f"{viz_type} should use plural metrics"
+            assert metrics == [{"label": "plural_metric"}], (
+                f"{viz_type} should use plural metrics"
+            )
 
     def test_pop_kpi_uses_singular_metric(self):
         """Test that pop_kpi (BigNumberPeriodOverPeriod) uses singular metric."""