[dajiaohuang]

Summary

Preserve the precision of fractional values in BarChart value labels so the annotations match the data used to draw each bar.

Related issue

Closes #654

Changes

• Keep the existing compact one-decimal formatter for axis tick labels.
• Use a precision-preserving formatter for data value labels.
• Add a focused contract regression test for fractional values.

Testing

• npx tsc --noEmit --pretty false (pass)
• python -m pytest tests/contracts/test_bar_chart_format_contract.py -q (pass)
• The full contract suite reached 1,199 passed and 7 skipped; 12 unrelated tests require the unavailable google.genai package.

Checklist

• The change is focused on a single logical concern.
• I ran the relevant tests locally (make test-contracts / make test) where applicable; the suite is limited by the unavailable optional Google dependency noted above.
• I updated docs/README if behavior or usage changed; the existing chart contract remains unchanged.
• No unrelated files (build artifacts, local config) are included in the diff.

[calesthio]

Thank you for separating data-label precision from axis-tick formatting. Reviewed the complete diff against main 63d1087a. The existing K/M abbreviations remain, while smaller fractional values preserve their supplied precision. Validation: focused contract passed; additionally executed the actual production formatter in Node: 0.015, 0.0004 and 1.2345 remain exact, with 1200 still displayed as 1.2K. This is the preferred precise-label fix over #754; consolidate them rather than merging both.