types/vm/runner: JsString 布局补 size_of/offset_of 编译期锚（实测 32B、utf16_len@24，tag 并入载荷首字无独立索引字），eval fn-decl 抛后描述符改显式值读钉住，non-definable-global-var 复测全绿撤 skip 条目

crates/oxide_vm/tests/global_fn_decl_builtin_tests.rs

@@ -205,11 +205,12 @@ fn eval_fn_decl_with_function_no_partial_binding_creation() {
 
 #[test]
 fn eval_fn_decl_a_side_value_and_descriptor_preserved() {
-    // 抛后 A 侧保留：Infinity 仍为原常量（自相等），描述符不可写位不变。
+    // 抛后 A 侧保留：Infinity 属性值仍为原常量（显式值读），描述符不可写位不变。
     let s = eval_str(
         "try { eval('function Infinity(){}'); } catch (e) {} \
-         (Infinity === Infinity) + ':' + \
-         (Object.getOwnPropertyDescriptor(globalThis, 'Infinity').writable === false ? 'w-false' : 'w-true')",
+         var d = Object.getOwnPropertyDescriptor(globalThis, 'Infinity'); \
+         (d.value === Infinity) + ':' + \
+         (d.writable === false ? 'w-false' : 'w-true')",
     );
     assert_eq!(s, "true:w-false");
 }