The explorer fetches a safetensors set with its config and tokenizer;
the mirror gives out a version's manifest only once nothing is
downloading and every shard its index names is there, with each file's
sha256, which nodes check; mirror add takes several URLs; a repository
page is refused as a source.
Refs #2 (item 9).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>