The POLineItem model has both a required `name` and an optional `description`
field. The export was only rendering `name` (with description as a fallback),
dropping the optional description entirely when a name was present.
- PDF: renders description in smaller italic text below the item name
- XLSX: appends description on a new line within the cell (wrapText enabled)
- Row height in XLSX now accounts for the extra line when description exists
Fixes#8
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
