test262: $262 宿主对象最小绑定 + is not defined 判定白名单化

引擎侧：绑定 $262 宿主对象（evalScript/global/gc 可用，detachArrayBuffer/
createRealm/agent 抛 not supported 而非 ReferenceError），并加入编译期
已知全局表；引用 $262.* 的测试从全量 skip 转为真实执行。

runner 侧：is not defined 不再一票吞 skip——解析错误消息中的标识符名，
仅在缺失全局白名单（$262/structuredClone/queueMicrotask）内才按能力
缺失跳过；其余 is not defined 按真实失败计入，修复后应转 PASS 的
测试恢复可见。

crates/oxide_vm/src/bindings/mod.rs

@@ -737,6 +737,7 @@ pub fn bind_global_builtin_slots(core: &Arc<KernelCore>, session: &KernelSession
     bind_stub_globals(core, session, global);
     bind_bigint::bind_bigint(core, session, global);
     bind_global_functions(core, session, global);
+    crate::test262_host::bind_test262_host(core, session, global);
     let global_this = JsValue::from_js_object(global as *mut JsObject);
     bind_existing_global(core, global, "globalThis", global_this);
 }
@@ -825,5 +826,6 @@ pub fn init_kernel_builtins(core: &Arc<KernelCore>, session: &mut KernelSession)
     bind_reflect::bind_reflect(core, session, global);
     bind_global::bind_global(core, session, global);
     bind_global_value(core, global, "globalThis", JsValue::from_js_object(global_ptr));
+    crate::test262_host::bind_test262_host(core, session, global);
     session.record_snapshot();
 }