mesh: merge plans, duplicate and crack checks, reverse Cuthill-McKee order (#234)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/mesh/src/lib.rs

@@ -13,6 +13,7 @@ pub mod delaunay;
 pub mod hex;
 pub mod join;
 pub mod mirror;
+pub mod nodes;
 pub mod octree;
 pub mod planar;
 pub mod quad;