`cargo xtask step-corpus --iges` (and `solvecraft-cli step-corpus --iges`) opens every oracle part.igs as File → Open does and compares body count, volume, area and face count with Fusion's measurements, writing docs/iges-import.md. The run found faces closing at an apex (a drill point's cone, a sphere's pole: the seam runs out to the apex and straight back) kept whole and meshed wrongly; they are now split along the iso-line opposite the seam like bands are (18-hole-features and 40-box-sphere-torus pass). The one failure left, 50-sweep-tight-bend, is written by Fusion as five loose, partly degenerate surfaces that Fusion cannot read back as a solid either; documented in the report. Test: a drilled blind hole round-trips through IGES.
Fixes#14
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT
