Relevant test:

• polygonize_preserves_enclosed_taiwan_polygon_minimal_matches_fixture a small repro case. The initial polygons cover Taiwan, and the output polygons do not.
• src/graph/topology_cleanup.rs the proposed fix

Root cause in split_touching_boundary_polygon: the split_faces.len() >= 2 branch assumes the extracted minimal edge rings fully tile the original polygon body. That assumption only holds when the body is simply connected (one connected component). For a polygon with holes whose body is multiply-connected (exterior — holes forms one piece), the body cannot be represented as a single minimal edge ring and the extracted sub-faces only cover "pockets" between touching holes; the bulk of the body is silently discarded.

Fix (src/graph/topology_cleanup.rs): gate the >= 2 split branch on the original polygon's interior_point() being covered by at least one split face. When the coverage check fails on a holed polygon, fall back to select_non_touching_holes, which preserves the exterior.