`quality::conformity` checks a solid mesh for cracks: the free faces must
close up (every corner edge on exactly two), no two distinct nodes may
coincide, and every element edge has one mid-side node. The hex tests
assert it for every method, hex20 included, and the crank arm sample's
7274 hex20 is conforming (#260: the disjoint lines are a display issue).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo
