Switch spine-prototype demo to fa_terrain_v1 atlas

Replaces the inline color-only demo_tilemap with a dep on the
prototype-fa-starter asset lib and its baked fa_terrain_v1 atlas.
The map atlases[] alias-string is updated to fa_terrain_v1; the
packed-u32 layer-tiles keep their numeric values because the baker
assigned the expected IDs (1 for grass_field surface tile, 2 for
stone_wall_brick wall tile). Adds maps.load_textures() call in init.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/tiles/demo_tilemap.tilemap.json

@@ -1,8 +0,0 @@
-{
-  "id": "demo_tilemap",
-  "tile_size": 32,
-  "tiles": [
-    {"id": "grass", "walkable": true,  "color": [110, 170, 80]},
-    {"id": "stone", "walkable": false, "color": [120, 120, 120]}
-  ]
-}

init.lua

@@ -9,6 +9,7 @@ local command    = require("lib-core.command")
 
 local demo_map = maps.load("maps/demo.map.json")
 maps.set_current(demo_map)
+maps.load_textures(engine.module.asset_aliases())
 
 local m_size = maps.size()
 local t_size = maps.tile_size()

manifest.module

@@ -5,14 +5,18 @@
     "api": "^0.1",
     "ci_frames": 30,
     "entry_point": "init.lua",
+    "asset_aliases": {
+        "fa_terrain_v1": "lib-asset.prototype-fa-starter"
+    },
     "deps": [
-        {"id":"lib-core.maps","version":"0.2.0"},
+        {"id":"lib-core.maps","version":"0.3.0"},
         {"id":"lib-core.render","version":"0.1.0"},
         {"id":"lib-core.camera","version":"0.3.0"},
         {"id":"lib-core.selection","version":"0.1.0"},
         {"id":"lib-core.input","version":"0.4.0"},
         {"id":"lib-core.player_control","version":"0.1.0"},
         {"id":"lib-core.interaction","version":"0.1.0"},
-        {"id":"lib-core.command","version":"0.1.0"}
+        {"id":"lib-core.command","version":"0.1.0"},
+        {"id":"lib-asset.prototype-fa-starter","version":"0.2.0"}
     ]
 }

maps/demo.map.json

@@ -2,7 +2,7 @@
   "schema_version": 2,
   "id": "demo",
   "size": { "w": 16, "h": 16 },
-  "atlases": ["demo_tilemap"],
+  "atlases": ["fa_terrain_v1"],
   "layers": {
     "surface": {
       "tiles": [