fix: minor stuff

engine/math/Vec3.ts

@@ -33,6 +33,8 @@ export namespace Vec3 {
 
   export function normalize(v: Vec3): Vec3 {
     const len = length(v)
-    return len === 0 ? v : scale(v, 1 / len)
+    // Fresh zero (not the input alias) to keep the namespace-wide no-aliasing
+    // guarantee even on the degenerate case.
+    return len === 0 ? { x: 0, y: 0, z: 0 } : scale(v, 1 / len)
   }
 }