Function ed25519_sign 

pub fn ed25519_sign(sk: &Ed25519SecretKey, msg: &[u8]) -> Ed25519Signature

Sign a message with Ed25519 (pure mode, no prehashing).

This is RFC 8032 §5.1 – the original / canonical Ed25519 mode. Identical bytes to what was produced before this commit’s generic-core refactor; the existing pinned RFC 8032 §7.1 test vectors still pass byte-exact.