Download the single best EPD PDF per product and write epd-download.json.
Reads epd-products.json and epd-candidates.json (already EPD-filtered), selects the best-ranked candidate with a pdfUrl, downloads one PDF to /workspace/work/outputs/epds//, and writes /workspace/work/code/epd-download.json. Never invents EPD metadata or PDF bytes. Match workbook is produced by epd-build-library.