- Add cell_validation.py module for Excel data validation metadata extraction
- Implement get_data_validation_for_cell() and get_all_validation_ranges()
- Include validation metadata in read_data_from_excel responses automatically
- Add get_data_validation_info MCP tool for validation rule summaries
- Resolve range references in list validations to actual cell values
- Support all validation types: list, whole, decimal, date, time, textLength
- Include operators (between, notBetween, equal, greaterThan, etc.) in metadata
This allows LLMs to understand Excel validation constraints including
dropdown options, numeric ranges, date constraints, and text length limits.
