- a_faces_seam_stays_within_half_its_width_of_the_face checks Rotate
(Classic)'s branches too: No Shading keeps its paint, a gradient keeps
the gradient, and Diffuse shades its plane darker at some view.
- classic_revolves_seams_are_round checks each seam's reach as well as
its join, and covers a gradient.
- The Wireframe edge takes seam_stroke (the same stroke it built by hand).
- Docs: which seams went from miter to round and which already were;
the white-light difference from the 2026-10-17 comparison is expected,
not measured; the 3D area rows record the change; the performance note
says its measurement predates the Classic Rotate and Revolve paths.