Function decode 

pub fn decode<T: DeserializeOwned>(
    expected_version: u8,
    bytes: &[u8],
) -> Result<T, CodecError>

Decode a payload produced by encode, rejecting a version mismatch.

Returns CodecError::Version when the leading byte differs from expected_version — a stale reader fails loudly instead of parsing old bytes against a new struct layout. Returns CodecError::TrailingBytes when the body decodes but leaves surplus bytes unconsumed: for a versioned format that exists to catch drift, garbage appended to a valid record is a corruption signal, not something to silently discard.