GHSA-h37v-hp6w-2pp8: ml-dsa's UseHint function has off by two error when r0 equals zero

There’s a bug in the use_hint function where it adds 1 instead of subtracting 1 when the decomposed low bits r0 equal exactly zero. FIPS 204 Algorithm 40 is pretty clear that r0 > 0 means strictly positive, but the current code treats zero as positive. This causes valid signatures to potentially fail verification when this edge case gets hit.