Use case: precise-object-edit. Cohesive chess sprite atlas, six columns by
two rows, transparent background. Reference: original assets/masters/pieces.png.
Columns: king, queen, rook, bishop, knight, pawn. Top ivory, bottom charcoal.
Classic Staunton three-dimensional upright pieces viewed slightly from above,
matching heights and baselines, shallow elliptical bases, strong readable
silhouettes. Upper-left lighting, broad simple grayscale shading, clean edges,
visible dark-piece highlights. Distinct cross/crown/battlements/slit/horse/ball.
No board, labels, background, blur, chrome or large cast shadows. Designed to
remain clear at native 48px sprite size. Generated with built-in image generation.

The generated transparent atlas is pieces-revised.png. Optional deterministic
native conversion: python3 tools/prepare_3d_pieces.py, then
python3 tools/generate_pieceicons.py. SDK builds use the checked-in header.
