Blobs are stored under the repository name of the pull, which purl writes as one name (pkg:oci/library%2Fnginx). Package rules write it as a path, pkg:oci/library/nginx, and get mapped to that form; keys with an empty segment, a tag or digest, or a bare upstream/{name} prefix are refused. Named upstreams keep their prefix, also when containerd reaches them through ns. Homebrew bottles and Helm charts pulled over OCI fall under oci too, bottles under Homebrew's image name (openssl@3 is homebrew/core/openssl/3). Manifests live in the metadata cache and aren't touched.
Refs #306
