Every GEAdd4 and GEMulFloat24x4 checked its lanes for the cases it can't do and branched to a
fallback, a vector-to-scalar move and a branch per operation, about 14% of skinning. The unchecked
variants only collect those lanes; a vertex where any appears is skinned again with the checked ones.
The products use GEMulFloat24x4 (the same as a one-term GERowSum4 here), and the position's and
normal's add chains are interleaved. Skinning is about 20% faster.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>