Checked against Excel-cached TEXT() results in number- and text-format test workbooks: 226 of 352 TEXT cells mismatched before, 0 after.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
insert.checkbox existed but had no ribbon button, replaced existing values
with FALSE and was written to XLSX as an invalid number format. Now:
Insert > Checkbox (Cell Controls); empty cells start FALSE, other values
stay and display as General; toggling an emptied box checks it and only
checkbox cells toggle; Delete unchecks first, then removes the boxes; XLSX
reads and writes the checkbox as Excel's feature-property-bag cell control
([MS-XLSX] 2.1.22, 2.3.9, 2.4.99).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>