拆分图片画布素材拖拽桥接

新增素材拖拽桥接 hook，承接素材拖向画布或文件夹的全局 pointer 监听

恢复认证弹窗 portal 渲染，避免全屏画布遮住账号入口

优化画布背景设置面板，补回当前色、色域、色相、预设、HEX 和恢复默认

补充素材拖拽、认证弹窗和背景面板回归测试并更新文档与 TRACKING

src/components/auth/AuthGate.test.tsx

@@ -2,7 +2,7 @@
 
 import { act, render, screen, waitFor, within } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
-import { useState } from 'react';
+import { useEffect, useState } from 'react';
 import { afterEach, beforeEach, expect, test, vi } from 'vitest';
 
 import type { AuthSessionSummary, AuthUser } from '../../services/authService';
@@ -250,6 +250,16 @@ function AccountPanelProbe() {
   );
 }
 
+function AutoOpenLoginProbe() {
+  const authUi = useAuthUi();
+
+  useEffect(() => {
+    authUi?.openLoginModal();
+  }, [authUi]);
+
+  return <div>编辑器内容</div>;
+}
+
 test('auth gate keeps platform content visible when phone login is available', async () => {
   authMocks.getAuthLoginOptions.mockResolvedValue({
     availableLoginMethods: ['phone'],
@@ -266,6 +276,22 @@ test('auth gate keeps platform content visible when phone login is available', a
   expect(screen.queryByText('先登录账号，再同步你的冒险进度。')).toBeNull();
 });
 
+test('auth gate portals page-level login requests above fullscreen content', async () => {
+  const { container } = render(
+    <AuthGate>
+      <div className="image-canvas-editor">全屏画布</div>
+      <AutoOpenLoginProbe />
+    </AuthGate>,
+  );
+
+  expect(await screen.findByText('编辑器内容')).toBeTruthy();
+  const dialog = await screen.findByRole('dialog', { name: '账号入口' });
+
+  expect(container.querySelector('[role="dialog"]')).toBeNull();
+  expect(dialog.parentElement?.parentElement).toBe(document.body);
+  expect(dialog.parentElement?.className).toContain('z-[120]');
+});
+
 test('auth gate waits for refresh cookie rotation before exposing restored user content', async () => {
   let resolveToken!: (token: string) => void;
   const tokenPromise = new Promise<string>((resolve) => {

src/components/auth/PlatformAuthModalShell.test.tsx

@@ -8,7 +8,7 @@ import { PlatformAuthModalShell } from './PlatformAuthModalShell';
 test('renders auth modal shell with platform theme and auth card chrome', () => {
   const onClose = vi.fn();
 
-  render(
+  const { container } = render(
     <PlatformAuthModalShell
       title="账号入口"
       platformTheme="light"
@@ -22,6 +22,8 @@ test('renders auth modal shell with platform theme and auth card chrome', () =>
 
   const dialog = screen.getByRole('dialog', { name: '账号入口' });
 
+  expect(container.querySelector('[role="dialog"]')).toBeNull();
+  expect(document.body.contains(dialog)).toBe(true);
   expect(dialog.parentElement?.className).toContain('platform-theme--light');
   expect(dialog.className).toContain('platform-modal-shell');
   expect(dialog.className).toContain('platform-auth-card');

src/components/auth/PlatformAuthModalShell.tsx

@@ -55,7 +55,6 @@ export function PlatformAuthModalShell({
       closeVariant="platformIcon"
       closeOnBackdrop
       closeOnEscape={false}
-      portal={false}
       size={size}
       showHeader={showHeader}
       zIndexClassName={zIndexClassName}