Writes a per-face field 'bad_winding' = number of shared manifold edges whose
neighbour disagrees on winding direction (0 = consistent). Marks every face on a
winding seam so they can be visualized / thresholded, mirroring the Open Edges and
Degenerate Faces nodes (face_attributes + metadata + UI summary). Batch-capable.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>