When kit packs a ModelKit, it sets a CreatedAt timestamp in the OCI config blob (ModelDescriptor) but does not set the standard org.opencontainers.image.created annotation on the manifest itself.

Tools and registries that inspect OCI manifests for creation time (e.g. registry UIs, garbage collection policies, lifecycle management tooling) rely on the pre-defined OCI annotation org.opencontainers.image.createdand won't find it on ModelKits today.

Set org.opencontainers.image.created in the manifest annotations during pack, alongside the existing ml.kitops.modelkit.cli-version annotation in pkg/lib/filesystem/local-storage.go.

The value should be the current time in RFC 3339 format, per the OCI image spec.