V3 deterministic spreadsheet-to-CSV capability pack. By-value connector composition (service_kind=cli, no separate ingredient): the local xlsx2csv CLI converts the first worksheet of one XLSX workbook to UTF-8 CSV via the spreadsheet.to_csv catalog operation. Fixed-function and reproducible: the executor materializes the source workbook and owns the throwaway output directory, while xlsx2csv writes a fixed sheet.csv result that is captured as result.file_ref. Write-tier but approval=never: xlsx2csv writes only to an engine-managed output dir, exposes no arbitrary flags, and never streams workbook bytes through op-step values. Requires xlsx2csv on PATH (Debian/Ubuntu: apt install xlsx2csv; Python environments: pip install xlsx2csv). Local and no-egress.