Function store_key 

pub fn store_key(id: &WireArtifactId) -> String

Store key for a coordinate: {name}-{version}.znippy — the sealed name znippy itself writes (tillsynia-20260706.znippy, rust-dev-rhel8-1.97.1.znippy).

The namespace is deliberately ignored: a sealed bundle has no group coordinate, and folding one into the key would silently collide two different ids onto one blob.