Read, edit, or create Microsoft Excel `.xlsx` workbooks. Trigger this skill whenever the user mentions a spreadsheet, .xlsx file, workbook, sheet, formula, pivot table, or asks to extract tabular data, modify a sheet, or build a workbook from rows. Three execution paths: structured inspection, in-place cell edits, and create-from-scratch via openpyxl. Values starting with `=` are written as formulas; everything else is a literal value with type preserved (int / float / str / datetime).