Booleans: prism cuts whose walls only touch the target are exact (#1894)

Thanks @NOWN-DEV.

crates/kernel/src/lib.rs

@@ -131,6 +131,7 @@ mod thread_display_tests;
 #[cfg(test)]
 mod thread_tests;
 mod topo;
+mod touching_walls;
 mod tspline;
 #[cfg(test)]
 mod untouched_faces_tests;