Function extract_embedded_commit_signature

pub fn extract_embedded_commit_signature(
    commit: &Commit<'_>,
) -> PatientResult<EmbeddedCommitSignature>

Extract the embedded signature material from a commit.

VPR stores a base64-encoded JSON container in the commit’s gpgsig header that includes:

• signature (base64 raw 64-byte r||s)
• public_key (base64 SEC1 public key bytes)
• optional certificate (base64 of PEM or DER bytes)

If a certificate is present, this validates that it corresponds to the embedded public key.