M7b follow-up: real opening cut through the wall + host-wall attachment

[Rowee13]

M7b (Door/Window, v0.2.2) places a framed door/window Component on a picked wall face without cutting the wall — the kernel has no boolean/CSG and faces are single-loop (no holes), so the solid wall remains behind the frame (the accepted "no cut" tradeoff, decision D1).

Follow-ups to make an opening a real architectural feature:

• Real opening cut: re-tessellate the wall face into surrounding panels + reveals around the opening, or add a kernel boolean, so there is a physical hole (with jamb reveals) rather than an overlapping frame. Relates to parametric/editable walls (M7a follow-up: parametric/editable walls + draw-on-face + persist wall defaults #88).
• Along-wall snapping: center-of-wall, equal spacing, edge offsets when placing along the picked wall.
• Wall-thickness-driven depth: auto-set the opening depth from the picked wall's measured thickness (currently a fixed default, 100 mm).
• Attach opening to its host wall: so moving/erasing the wall carries or removes its openings.

Design: docs/2026-07-12-M7b-doorwindow-design.md (Out of scope section).