feat: game/engine split refactor + skybox

game/textures.ts

@@ -0,0 +1,23 @@
+import type { Texture } from "../engine/render/Texture"
+
+/** The game's texture palette -- the named surfaces content refers to (materials,
+ *  mobs, room). `app/assets.ts` loads the actual pixels via the DOM; this is the
+ *  shape both sides agree on, kept in `game/` so content never imports the browser
+ *  loader. Filenames in `/assets` are the contract. */
+export type Textures = {
+  floor: Texture
+  grass: Texture
+  bark: Texture
+  birch: Texture
+  leaf: Texture
+  needle: Texture
+  rock: Texture
+  flower: Texture
+  wall: Texture
+  crate: Texture
+  npc: Texture
+  frog: Texture
+  bee: Texture
+  robin: Texture
+  skybox: Texture
+}