3.1+ path. Structured references to product format_options[]
entries. Product-local options use { scope: 'product', format_option_id }; publisher-catalog-backed options use
{ scope: 'publisher', publisher_domain, format_option_id }.
Optionalformat_Legacy identifiers are deliberately unavailable on the canonical SDK surface.
Result shape for packageRefsForFormatOptions - spread into a
PackageRequestto author a canonical format-option package. The helper retains downgrade metadata in module-private weak storage.