Function verify_step_fact_transcript 

pub fn verify_step_fact_transcript(
    jsonl_path: &Path,
) -> Result<TranscriptVerified, VerifyError>

Verify a JSONL transcript file produced by JsonlFileSink.

Reads the file line-by-line, recomputes each line’s SHA-256, and checks that prev_hash matches the previous line’s hash.

Errors

Returns VerifyError for any I/O failure, malformed line, or chain break.