feat(maps): v0.5.4 — atlas_diffuse_handle + atlas_tile_size_px + atlas_tile_uv

Public accessors for palette-like consumers (map-editor 0.2.0c.2)
that need to render real tile thumbnails. All three return nil when
the atlas-idx is out of range, the slot has no tile in the atlas,
or the texture failed to load (headless test env).

atlas_tile_uv resolves the slot via the same `slot_NN_` regex used
internally by the v3 vertex/material render path, so callers see
the same slot -> tile_id mapping the renderer uses.

init.lua

@@ -1210,6 +1210,38 @@ function M.atlas_id_at(idx, map_id)
         or m.atlases[idx + 1] and m.atlases[idx + 1].id
 end
 
+-- 0.5.4: Public accessors for palette-like consumers (map-editor) that
+-- need to render real tile thumbnails. All three return nil when the
+-- atlas-idx is out of range, the slot has no tile in the atlas, or the
+-- texture failed to load (headless test env).
+function M.atlas_diffuse_handle(atlas_idx, map_id)
+    local id = map_id or current_map_id
+    if not id then error("maps.atlas_diffuse_handle: no current map") end
+    local m = map_registry[id]
+    local atlas = m.atlases and m.atlases[atlas_idx + 1]
+    return atlas and atlas.diffuse_texture_handle or nil
+end
+
+function M.atlas_tile_size_px(atlas_idx, map_id)
+    local id = map_id or current_map_id
+    if not id then error("maps.atlas_tile_size_px: no current map") end
+    local m = map_registry[id]
+    local atlas = m.atlases and m.atlases[atlas_idx + 1]
+    return atlas and atlas.tile_size_px or nil
+end
+
+function M.atlas_tile_uv(atlas_idx, slot, map_id)
+    local id = map_id or current_map_id
+    if not id then error("maps.atlas_tile_uv: no current map") end
+    local m = map_registry[id]
+    local atlas = m.atlases and m.atlases[atlas_idx + 1]
+    if not atlas or not atlas.tiles then return nil end
+    local slot_idx = atlas_slot_index(atlas)
+    local tile_id = slot_idx[slot]
+    local tile = tile_id and atlas.tiles[tile_id]
+    return tile and tile.uv or nil
+end
+
 function M.has_layer(layer_name, map_id)
     local id = map_id or current_map_id
     if not id then error("maps.has_layer: no current map") end