testkit: run the meshing skill on the corpus and samples (cargo xtask skill-results)

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

crates/engine/src/cmd/mod.rs

@@ -19,6 +19,7 @@ pub use datum::edit_params as datum_edit_params;
 pub use datum::preview as datum_preview;
 pub use mesh::analytic_surfaces;
 pub use nodes::merge_preview as node_merge_preview;
+pub use plan::untagged_faces;
 pub use relax::{Preview as RelaxPreview, preview as relax_preview, sphere as relax_sphere};
 mod mirror;
 mod model;