Implements Task 3 (World: spawn/despawn, add/get/remove components, query/query2 with type-erased HashMap<TypeId, Box<dyn ComponentStorage>>) and Task 4 (Transform: position/rotation/scale with matrix() building T*RotY*RotX*RotZ*S). 25 tests pass. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>