Deterministic Q48.16 fixed-point math, the same bits on every platform.
- fixNormalize lifts short vectors into range before dividing: results are unit within fixIsNormalized's tolerance at every input magnitude, down to a raw length of 1, with direction preserved bit for bit.
- The vector-layer reductions (fixDotRaw, fixFromDotRaw, fixDotQuat, fixMulQuat, fixInvMulQuat) join fixMul in spelling their expressions in bare native operators where __int128 exists, eliminating the seam-call stack traffic that dominates unoptimized builds — bit-identical on both arms.