Adds SurfaceNetsTests.cs and QuadNormalsTests.cs covering the sign
convention, edge naming, outward winding, vertex placement (midpoint and
unequal-crossing means, origin/cellSize), closed-sphere welding and
Euler characteristic, an ambiguous checkerboard cell's even-but-not-2 edge
usage, open-boundary quad suppression, determinism/ordering, and
face-weighted normals (sliver-vs-large-quad area weighting, unit cube
normals, zero-area/untouched-vertex degenerate case). Adds
stryker-config.json (vstest runner; this project is NUnit 4, not xunit.v3)
and records GameCult.Geometry as scoped, diff-only, in
docs/mutation-testing.md's follow-ups.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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