Function run_compute_id 

async fn run_compute_id<ObjectID: FsVerityHashValue>(
    repo: &Repository<ObjectID>,
    image: String,
    verity: Option<String>,
    bootable: bool,
) -> Result<OciComputeIdReply, OciError>

Compute the composefs image ID for an OCI image.

Mirrors the CLI compute-id path: digest references (@sha256:…) use the supplied verity override, while named refs derive both the config digest and verity from the stored image metadata (ignoring verity).