fix: a hole placed on a face follows the face along its axis only, and warns when off the face (#510)

A hole positioned on a face now follows that face along the hole's own axis instead of sliding to the face's nearest point. When the face no longer reaches the position, the hole stays where it was placed and the feature says so.

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

crates/engine/src/lib.rs

@@ -795,6 +795,8 @@ mod delete_face_tests;
 #[cfg(test)]
 mod extent_tests;
 #[cfg(test)]
+mod hole_face_tests;
+#[cfg(test)]
 mod naming_history_tests;
 #[cfg(test)]
 mod pattern_suppress_tests;