feat: actors stage 2

tests/mobs.test.ts

@@ -0,0 +1,21 @@
+import { expect, test } from "bun:test"
+import { MOB_KINDS, Mob } from "../engine/scene/Mob"
+
+// The mob SAB packs a kind as its index in MOB_KINDS; the main thread and every
+// render worker must agree on that order. Freeze it here: appending a kind is fine,
+// but reordering or removing an existing one silently corrupts which mesh/texture a
+// worker draws.
+test("MOB_KINDS order is frozen (mob SAB ids)", () => {
+  expect(MOB_KINDS).toEqual(["frog", "bee", "robin"])
+})
+
+test("every kind resolves to a complete definition", () => {
+  for (const kind of MOB_KINDS) {
+    const d = Mob.def(kind)
+    expect(d.name).toBe(kind)
+    expect(typeof d.build).toBe("function")
+    expect(typeof d.update).toBe("function")
+    expect(d.boundingRadius).toBeGreaterThan(0)
+    expect(d.bodyHeight).toBeGreaterThan(0)
+  }
+})