The "JSON, images" Mac Studio GGUF CI job hit a stale cache for
${{ runner.os }}-gguf-...-mmproj-F16.gguf-v1 that contains only the
main GGUF, not the mmproj sibling. cache-hit==true so the download
step was skipped, then the post-load \`ls\` failed:
ls: ...gguf-cache/mmproj-F16.gguf: No such file or directory
Three guards layered:
1) Bump cache key v1 -> v2 to invalidate the poisoned entry on the
GitHub-hosted side.
2) New verify-cache step explicitly checks BOTH files are present
before trusting cache-hit. If not, fall through to download.
3) Save step gains a hashFiles() check on the mmproj path so a
partial mmproj download cannot land back in the cache.
Behaviour on a clean run is unchanged; cache hit + verify ok skips
the re-download, partial-hit triggers fresh download, success
saves a complete archive.