Separate model payload hashes from downloader cache metadata

A pinned model snapshot receipt should bind substantive checkpoint and configuration files, but downloader cache metadata is not a stable part of the model identity. Client versions can rewrite cache metadata while resolving the same pinned revision and identical payload bytes. Keep the signed inventory for audit, explicitly classify cache-control files as non-binding, and fail closed on every substantive-file mismatch. This preserves reproducibility without making the receipt depend on one downloader implementation.

Applies when: verifying locally materialized Hugging Face snapshots against pinned revisions. Keywords: Hugging Face snapshot receipt cache metadata model hash revision reproducibility