New command inspect.compare {a, b, tolerance?}: measures of both and their differences, two-way surface deviation from a bounding-volume tree, regions beyond the tolerance clustered by side (only_in_a / only_in_b) with integrated volumes and faces, a verdict, optional face colouring as one undo step, and warnings for open meshes. Geometry in solidcraft-geom (compare.rs), command in the engine. Closes#1363.