Function safety_code 

pub fn safety_code(public_key: &[u8; 32]) -> String

huddle 0.7.8: 12-hex Safety Code derived from the same SHA-256 of the Ed25519 pubkey that backs compute_fingerprint. Format SAFE-XXXX-XXXX-XXXX (uppercase, dash-separated). Display-only — a shorter, less ambiguous handle to compare against a friend at the start of a session.