Formula cells should inherit number format from referenced cells

[arcaputo3]

Problem

When a formula references cells with number formatting (e.g., currency), Excel automatically inherits that formatting for the result cell. Currently, xl does not do this - formula cells get General format regardless of their inputs.

Example:

[
  {"op": "put", "ref": "B2", "value": 1000000, "format": "currency"},
  {"op": "put", "ref": "B3", "value": 600000, "format": "currency"},
  {"op": "putf", "ref": "B4", "value": "=B2-B3"}
]

Current behavior: B4 shows 400000 (General format)
Expected behavior: B4 shows $400,000.00 (inherited Currency format)

Workaround

Explicitly style formula cells:

{"op": "putf", "ref": "B4", "value": "=B2-B3"},
{"op": "style", "range": "B4", "numFormat": "currency"}

Proposed Solution

1. Parse the formula to extract cell references
2. Look up styles of referenced cells
3. Determine "dominant" format using Excel's precedence rules:
   • Currency > Percent > Date > Decimal > General
   • If mixed incompatible formats, use General
4. Apply the dominant format to the formula cell

Scope

This would affect:

• BatchParser.applyPutFormula()
• WriteCommands.putFormula()
• Potentially the streaming writer

Priority

Nice-to-have for Excel parity, but the explicit styling workaround is reasonable for now.