M2: shell and draft (exact convex polyhedra from planes)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/kernel/src/lib.rs

@@ -17,6 +17,7 @@ mod body;
 mod build;
 mod measure;
 mod ops;
+mod polyhedron;
 mod step;
 mod topo;
 
@@ -25,6 +26,7 @@ pub use body::{Body, EdgeInfo, FaceInfo};
 pub use build::{box_solid, cylinder, extrude, extrude_tapered, revolve, sphere, torus};
 pub use measure::{BodyMeasure, measure};
 pub use ops::{BoolOp, boolean, split_by_plane, transform, transform_matrix};
+pub use polyhedron::{HalfSpace, convex_polyhedron, draft, shell};
 pub use step::step_export;
 pub use topo::{TopoCounts, merged_topology, seam_flags};