Make load_textures iterate atlases for v2 maps

M.load now auto-upgrades v1 maps to v2 shape (no m.tilemap field), but
load_textures still dereferenced m.tilemap unconditionally and crashed on
every v2 consumer. Extract per-tilemap loop into a helper and dispatch by
schema_version.

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

init.lua

@@ -595,13 +595,7 @@ end
 -- Operates on the current map's tilemap; call after maps.set_current.
 -- asset_aliases: { [alias-key] = asset-lib-id } from module's manifest.
 -- ====================================================================
-function M.load_textures(asset_aliases)
-    local map_id = M.current()
-    if map_id == nil then
-        error("maps.load_textures: no current map; call maps.set_current first")
-    end
-    local m = map_registry[map_id]
-    local tm = m.tilemap
+local function load_textures_for_tilemap(tm, asset_aliases)
     if tm.asset_pack == nil then return end  -- color-only tilemap, no textures
     local lib_id = asset_aliases[tm.asset_pack]
     if lib_id == nil then
@@ -627,6 +621,23 @@ function M.load_textures(asset_aliases)
     end
 end
 
+function M.load_textures(asset_aliases)
+    local map_id = M.current()
+    if map_id == nil then
+        error("maps.load_textures: no current map; call maps.set_current first")
+    end
+    local m = map_registry[map_id]
+
+    if m.schema_version == 2 then
+        for _, tm in ipairs(m.atlases) do
+            load_textures_for_tilemap(tm, asset_aliases)
+        end
+        return
+    end
+    -- v1 legacy: kept for M.create with manual v1 table
+    load_textures_for_tilemap(m.tilemap, asset_aliases)
+end
+
 function M.iterate_layers_pre_entities(fn, map_id)
     local id = map_id or current_map_id
     if not id then error("maps.iterate_layers_pre_entities: no current map") end