iter(g57): form 校验支持异步规则

apps/demo/main.ts

@@ -150,6 +150,7 @@ const modalOpen = signal(false);
 const modalPick = signal('a'); // 弹窗内下拉的取值，用于演示 Esc 逐层关闭
 
 // —— 表单校验状态集中声明 ——
+const inviteCode = signal(''); // 异步校验演示：邀请码
 const username = signal('');
 const email = signal('');
 const formResult = signal('');
@@ -398,13 +399,17 @@ const content = h(
   section(
     'sec-formlab',
     '表单校验',
-    'form + formItem：必填 / 长度 / 正则校验，全部通过才触发提交；失焦校验、输入清错。',
+    'form + formItem：必填 / 长度 / 正则同步校验，validator 返回 Promise 即异步规则（提交会等待）；全部通过才触发提交。',
     form(
       { submitText: '注册', onSubmit: () => formResult(`提交成功：${username()} / ${email()} / ${city()}`) },
       [
         formItem({ label: '用户名', required: true, value: username, rules: [{ min: 2, max: 12, message: '用户名需 2-12 个字符' }] }, textField({ placeholder: '2-12 个字符', value: username })),
         formItem({ label: '邮箱', required: true, value: email, rules: [{ pattern: /^[\w.-]+@[\w-]+\.[\w.]+$/, message: '邮箱格式不正确' }] }, textField({ placeholder: 'you@example.com', value: email })),
         formItem({ label: '城市', required: true, value: city }, select({ options: cities.map((c) => ({ value: c, label: c })), value: city, placeholder: '请选择城市…' })),
+        formItem(
+          { label: '邀请码', required: true, value: inviteCode, rules: [{ validator: async (v) => { await new Promise((r) => setTimeout(r, 400)); return v === 'USED' ? '该邀请码已被使用' : true; }, message: '校验未通过' }] },
+          textField({ placeholder: '异步规则：输入 USED 会校验失败', value: inviteCode }),
+        ),
       ],
     ),
     h('span', { class: 'out' }, () => formResult() || '等待提交…'),