Feat: add cell type coercion for Excel export

[huang-aoqin]

What problem does this PR solve?

• Implemented a helper function to convert markdown cell text to native numeric types for Excel output.
• Ensured that leading zeros are preserved and handled various numeric formats, including those with thousand separators and scientific notation.

Type of change

• New Feature (non-breaking change which adds functionality)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.72%. Comparing base (456b1bb) to head (280e40d).
⚠️ Report is 166 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #13808       +/-   ##
===========================================
+ Coverage   48.72%   96.72%   +48.00%     
===========================================
  Files          45       10       -35     
  Lines        9895      702     -9193     
  Branches      112      112               
===========================================
- Hits         4821      679     -4142     
+ Misses       5064        5     -5059     
- Partials       10       18        +8     

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