The decoder documented 736 bytes and accepted anything from 544 up, leaving
whichever of the five evaluations were missing at zero. A truncated proof
therefore decoded as a well-formed one carrying values nobody sent, and the
comment explaining it said the scalars were optional in some formats without
naming one. It now takes exactly the size it describes, and refuses trailing
bytes for the reason they are refused elsewhere here: bytes the format does not
describe are bytes two different proofs can differ in.
Also removes bytesReader, which nothing called.
Co-authored-by: Hanzo Dev <[email protected]>