继续收口认证入口弹窗壳层

新增 PlatformAuthModalShell 统一认证白底弹窗壳层

登录入口和邀请码弹窗复用共享认证壳层

补充认证壳层和 AuthGate 接入测试

同步 PlatformUiKit 文档和 Hermes 决策记录

src/components/auth/PlatformAuthModalShell.test.tsx

@@ -0,0 +1,54 @@
+/* @vitest-environment jsdom */
+
+import { fireEvent, render, screen, within } from '@testing-library/react';
+import { expect, test, vi } from 'vitest';
+
+import { PlatformAuthModalShell } from './PlatformAuthModalShell';
+
+test('renders auth modal shell with platform theme and auth card chrome', () => {
+  const onClose = vi.fn();
+
+  render(
+    <PlatformAuthModalShell
+      title="账号入口"
+      platformTheme="light"
+      onClose={onClose}
+      closeLabel="关闭登录弹窗"
+      panelClassName="!max-w-md"
+    >
+      <div>登录表单</div>
+    </PlatformAuthModalShell>,
+  );
+
+  const dialog = screen.getByRole('dialog', { name: '账号入口' });
+
+  expect(dialog.parentElement?.className).toContain('platform-theme--light');
+  expect(dialog.className).toContain('platform-modal-shell');
+  expect(dialog.className).toContain('platform-auth-card');
+  expect(dialog.className).toContain('!max-w-md');
+  expect(within(dialog).getByText('登录表单')).toBeTruthy();
+
+  fireEvent.click(dialog.parentElement as HTMLElement);
+  expect(onClose).toHaveBeenCalledTimes(1);
+});
+
+test('keeps escape disabled for auth flows', () => {
+  const onClose = vi.fn();
+
+  render(
+    <PlatformAuthModalShell
+      title="请填写邀请码"
+      platformTheme="dark"
+      onClose={onClose}
+      closeLabel="取消填写邀请码"
+      zIndexClassName="z-[130]"
+    >
+      <div>邀请码表单</div>
+    </PlatformAuthModalShell>,
+  );
+
+  fireEvent.keyDown(window, { key: 'Escape' });
+
+  expect(onClose).not.toHaveBeenCalled();
+  expect(screen.getByRole('button', { name: '取消填写邀请码' })).toBeTruthy();
+});