feat: 迭代器原型基建：%IteratorPrototype% 链 + 各集合迭代器原型

新增 %IteratorPrototype%（含 @@iterator 返回自身，经原型链被全部迭代器
继承，it[Symbol.iterator]() === it 恒等）与 %ArrayIteratorPrototype%/
%MapIteratorPrototype%/%SetIteratorPrototype%/%StringIteratorPrototype%/
%RegExpStringIteratorPrototype%（链到 %IteratorPrototype%）；Array/Map/Set/
TA/String/matchAll 迭代器包装统一挂对应原型；补 Array/String 的 @@iterator
别名绑定。集合迭代器原型不含 return 方法（规范集合迭代器无 return）。

crates/oxide_builtins/src/map.rs

@@ -326,6 +326,7 @@ pub fn map_entries<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     NativeResult::Ok(crate::iterator::make_mode_iterator(
         vm,
         this_val,
+        JsValue::from_js_object(vm.session().builtin_world().map_iterator_proto.as_ptr() as *mut JsObject),
         crate::iterator::map_entries_iter_next::<H> as *const (),
     ))
 }
@@ -337,6 +338,7 @@ pub fn map_values<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     NativeResult::Ok(crate::iterator::make_mode_iterator(
         vm,
         this_val,
+        JsValue::from_js_object(vm.session().builtin_world().map_iterator_proto.as_ptr() as *mut JsObject),
         crate::iterator::map_values_iter_next::<H> as *const (),
     ))
 }
@@ -348,6 +350,7 @@ pub fn map_keys<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     NativeResult::Ok(crate::iterator::make_mode_iterator(
         vm,
         this_val,
+        JsValue::from_js_object(vm.session().builtin_world().map_iterator_proto.as_ptr() as *mut JsObject),
         crate::iterator::map_keys_iter_next::<H> as *const (),
     ))
 }