refactor: move world concepts into engine

game/actors/Bush.ts

@@ -1,5 +1,7 @@
 import type { Vec3 } from "../../engine/math/Vec3"
 import { STRIDE, type Mesh } from "../../engine/scene/Mesh"
+import type { Material } from "../../engine/render/Material"
+import type { Prefab } from "../../engine/scene/Prefab"
 
 const TAU = Math.PI * 2
 
@@ -17,6 +19,13 @@ export type Bush = {
  *  wound outward, so backface culling is safe. `build` appends into a shared
  *  (leaf-textured) mesh. */
 export namespace Bush {
+  export function create(material: Material): Prefab<Bush> {
+    return {
+      position: (bush) => bush.position,
+      bakeNear: (bush, batch) => build(bush, batch.mesh(material)),
+    }
+  }
+
   export function build(bush: Bush, mesh: Mesh): void {
     const rand = rng(bush.seed)
     // A handful of smaller overlapping lumps reads as a soft shrub; one big
@@ -34,7 +43,14 @@ export namespace Bush {
   }
 
   /** A small lumpy low-poly sphere, wound outward (matches the oak canopy blob). */
-  function blob(mesh: Mesh, cx: number, cy: number, cz: number, radius: number, rand: () => number): void {
+  function blob(
+    mesh: Mesh,
+    cx: number,
+    cy: number,
+    cz: number,
+    radius: number,
+    rand: () => number,
+  ): void {
     const seg = 6
     const rings = 4
     const start = mesh.verts.length / STRIDE