Function blake3_hash_auto 

pub fn blake3_hash_auto(region: &[u8]) -> Hash

Compute an unkeyed BLAKE3 hash, automatically dispatching to the multi-thread update_rayon path when the input is large enough to benefit. See BLAKE3_RAYON_THRESHOLD. Used by both Blake3Signer (sign side) and Blake3DigestVerifier (verify side) so that a single-call API “just gets faster” on large inputs without callers needing to pick a code path.