fix: coincident faces are pushed apart only where that changes nothing (#817)

A coincident face is pushed apart only when the space it moves through holds nothing that changes the result; otherwise the boolean falls through to the exact strategies.

Co-authored-by: NOWN-DEV <257771410+NOWN-DEV@users.noreply.github.com>

crates/kernel/src/lib.rs

@@ -21,6 +21,7 @@ mod boolean_guard;
 mod boolean_record;
 mod bore_guard;
 mod build;
+mod clearance;
 mod coplanar;
 mod curveblend;
 mod delete_face;