fix(mcp): expose table column formatting

[aminghadersohi]

SUMMARY

Expose per-column table formatting in MCP chart configurations. Table configs can set columnWidth, d3NumberFormat, and d3TimeFormat, keyed by result column label, and the generated schema documents concrete D3 format examples.

Existing table column_config values are preserved when an update omits the field, while explicit values are validated and serialized without silently dropping unknown settings.

TESTING INSTRUCTIONS

pytest -q tests/unit_tests/mcp_service/chart/test_new_chart_types.py tests/unit_tests/mcp_service/chart/tool/test_get_chart_type_schema.py tests/unit_tests/mcp_service/chart/tool/test_update_chart.py tests/unit_tests/mcp_service/chart/tool/test_update_chart_preview.py
uvx pre-commit run --files superset/mcp_service/chart/chart_utils.py superset/mcp_service/chart/schemas.py superset/mcp_service/chart/tool/update_chart.py superset/mcp_service/chart/tool/update_chart_preview.py tests/unit_tests/mcp_service/chart/test_new_chart_types.py tests/unit_tests/mcp_service/chart/tool/test_get_chart_type_schema.py tests/unit_tests/mcp_service/chart/tool/test_update_chart.py tests/unit_tests/mcp_service/chart/tool/test_update_chart_preview.py

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration
• Introduces new feature or API
• Removes existing feature or API

BLAST RADIUS

Limited to MCP table chart configuration schemas and form-data mapping. It does not change authorization, database models, migrations, or non-MCP chart behavior.

RISK AND ROLLBACK

The main risk is accepting a formatting value that the frontend renders differently than expected. Validation constrains field names and primitive types, and rollback is a normal revert with no data migration.

REVIEW GUIDANCE

Start with TableColumnConfig in schemas.py, then review the form-data mapping and preservation paths in the two update tools.

EVAL EVIDENCE

The deterministic schema and round-trip paths are covered by 189 passing focused MCP unit tests. No model-based evaluation suite was available in this checkout.

COST AND LATENCY DELTA

No prompt, model, routing, or tool-call changes. The added local schema validation and dictionary serialization have negligible request cost and latency impact.

PROMPT / NON-DETERMINISM

No prompt or non-deterministic behavior changed.

[codecov]

Codecov Report

❌ Patch coverage is 31.57895% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.44%. Comparing base (035eaa8) to head (8d95b8f).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
superset/mcp_service/chart/tool/update_chart.py	0.00%	7 Missing ⚠️
...set/mcp_service/chart/tool/update_chart_preview.py	0.00%	4 Missing ⚠️
superset/mcp_service/chart/chart_utils.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #42658      +/-   ##
==========================================
- Coverage   65.44%   65.44%   -0.01%     
==========================================
  Files        2810     2810              
  Lines      159366   159381      +15     
  Branches    36374    36379       +5     
==========================================
+ Hits       104302   104308       +6     
- Misses      53022    53031       +9     
  Partials     2042     2042              

Flag	Coverage Δ
hive	38.09% <31.57%> (+<0.01%)	⬆️
mysql	57.82% <31.57%> (-0.01%)	⬇️
postgres	57.87% <31.57%> (-0.01%)	⬇️
presto	39.98% <31.57%> (ø)
python	59.25% <31.57%> (-0.01%)	⬇️
sqlite	57.49% <31.57%> (-0.01%)	⬇️
unit	100.00% <ø> (ø)

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