chore(maps): bump to 0.5.7; README cell-tile path subsection

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -5,7 +5,7 @@ Multi-layer tile-grid map implementation with vertex-painted autotile
 loading + UV resolution, walkability + sight-blocking queries, and a
 v3 multi-layer render pipeline with opaque-ceiling cache.
 
-**Version:** 0.5.6
+**Version:** 0.5.7
 **Lib-ID:** lib-core.maps
 **Requires:** (none)
 **Tags:** maps, tile-grid, multi-layer, vertex-painting, autotile, blob-14, override, walkability, tilemap
@@ -47,6 +47,30 @@ other as material whenever any unrelated corner of either was painted,
 producing connected blobs across visually empty paint-tile gaps. See
 plan `2026-05-29-painting-model-rethink`.
 
+### Cell-Tile material path (0.5.7)
+
+A second, optional painting path: each layer can now also have a
+`cells_material` array (W·H bool, lazy-allocated). Cells where
+`cells_material[x, y]` is set use the classical 47-blob 8-neighbour
+bitmask rule on effective material (vertex-derived OR cell-derived),
+unlocking all 14 atlas slots. Cells whose material comes only from
+the vertex grid continue to use the FIX-A 4-own-corner rule (5
+reachable slots, dual-grid look).
+
+Both paths coexist in the same layer; the bitmask rule is decided
+per-cell based on whether `cells_material[x, y]` is true. A
+vertex-only cell adjacent to a cell-tile cell remains structurally
+blind to its neighbour because its 4-corner rule only reads its own
+corner vertices — this asymmetric seam is documented behaviour. For
+clean visuals use a single painting path per layer.
+
+Public API: `set_cell_material(layer, x, y, painted, map_id?)` and
+`get_cell_material(layer, x, y, map_id?) -> bool`.
+
+The `cells_material` field is optional and absent on every existing
+v3 map; save output is byte-identical to 0.5.6 when no cells_material
+entries are non-zero.
+
 ## Topology
 
 <!-- topology:start (auto-generated; do not edit) -->