统一修复Modal Portal主题继承

在UnifiedModal集中解析Portal主题并支持显式覆盖
梳理危险确认、图片预览、报告和工具弹窗的主题边界
修复固定浅色画布弹窗与Agent菜单的主题回归
将相关公共组件测试纳入默认Vitest收集范围
同步Platform UI Kit、画布Agent与共享记忆文档

src/components/common/PlatformToolModalShell.tsx

@@ -1,6 +1,5 @@
 import type { ReactNode } from 'react';
 
-import { useAuthUi } from '../auth/AuthUiContext';
 import { UnifiedModal } from './UnifiedModal';
 
 type PlatformToolModalShellProps = {
@@ -50,9 +49,6 @@ export function PlatformToolModalShell({
   bodyClassName,
   footerClassName,
 }: PlatformToolModalShellProps) {
-  const resolvedPlatformTheme =
-    useAuthUi()?.platformTheme ?? 'light';
-
   return (
     <UnifiedModal
       open={open}
@@ -68,7 +64,6 @@ export function PlatformToolModalShell({
       closeOnBackdrop={closeOnBackdrop}
       closeOnEscape={closeOnEscape}
       zIndexClassName={zIndexClassName}
-      overlayClassName={`platform-theme platform-theme--${resolvedPlatformTheme}`}
       panelClassName={joinClassNames(
         'platform-remap-surface shadow-[0_24px_80px_rgba(0,0,0,0.55)]',
         panelClassName,