Function validate_data_ref_structural 

pub fn validate_data_ref_structural(dr: &DataRef) -> Result<(), AcdpError>

Same as validate_data_ref but skips the embedded-content_hash recomputation. Callers that want to report per-DataRef hash failures (e.g. acdp::client::VerifiedContext::fetch_report) run the structural checks via this helper, then call verify_embedded_hash themselves and record the outcome instead of short-circuiting.