Module cleanup 

Post-CSG polygon cleanup: remove degenerate polygons, collapse collinear vertices, and merge coplanar adjacent polygons.

Functions

cleanup_polygons

Full cleanup pass: remove degenerates, collapse collinear vertices, merge coplanars.

is_degenerate

Returns true if a polygon is degenerate (near-zero area or duplicate vertices).

merge_coplanar_polygons

Merge coplanar adjacent polygons that share edges.

remove_collinear_vertices

Remove collinear interior vertices from a polygon.