Dara: simplify it further. The jambs either side of the window and the
frame's side posts still cast wedges into the room. The ruling's regions
now span the full width between the garage's side walls, and a wall only
takes the ruling when at least half of it lies inside a region, so the
garage's own corner walls stay solid.

Gate: all tests pass.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>