profile_assembly.py now checks each pocket's polyline against the plate
boundary using Shapely contains(). Pockets extending outside are dropped.
Sandbox 1: 1 pocket removed (was crossing corner near x=150, y=-20).
Brain: profile_assembly.py now exports 'rib_web' — the actual material
geometry from Shapely boolean (exterior + interior rings). This is the
rib shape, not the pocket cutouts.
import_profile.py: prefers rib_web when available, drawing exterior +
interior polyline rings directly. Falls back to pocket-based drawing
for older rib JSONs without rib_web.
