Imagination pass (session self-2026-10-10-ag): the cost-progress stop at
BoundedLeastSquares.cs:275 reports Converged with a bound still violated;
fix follows Lawson-Hanson. Quaternion algebra surface and the
mul(float4,float4) overload trap.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
