Function extract_layer_ids 

pub fn extract_layer_ids(
    manifest_json: &str,
    config_json: &str,
) -> Result<Vec<String>>

Extract ordered layer identifiers from raw manifest and config JSON.

For standard container images (ImageConfig media type), parses the config and returns rootfs.diff_ids. For OCI artifacts with non-standard config types, falls back to the manifest’s layer digests.

This is the high-level entry point for callers that have raw JSON strings (e.g. from a varlink Inspect reply).