refactor(glass): 批次3 - 迁移 AgentChat 页面使用统一毛玻璃配置

迁移以下 10 个 AgentChat 模块文件:
- index.js: GLASS_BLUR.lg 替换 blur(20px)
- LeftSidebar/index.js: GLASS_BLUR.lg/sm 替换 blur(20px)/blur(10px)
- LeftSidebar/SessionCard.js: GLASS_BLUR.md 替换 blur(12px)
- RightSidebar/index.js: GLASS_BLUR.lg/sm/md 替换多处硬编码
- RightSidebar/ToolSelector.tsx: GLASS_BLUR.md 替换 blur(12px)
- ChatArea/index.js: GLASS_BLUR.lg/sm 替换多处硬编码
- ChatArea/MessageRenderer.js: GLASS_BLUR.md 替换 blur(16px)
- ChatArea/WelcomeScreen.js: GLASS_BLUR.md 替换 blur(12px)
- ChatArea/ExecutionStepsDisplay.js: GLASS_BLUR.sm 替换 blur(10px)
- MeetingRoom/index.js: GLASS_BLUR.lg 替换 blur(20px)

保留 saturate(180%) 组合效果

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/views/AgentChat/components/ChatArea/WelcomeScreen.js

@@ -22,6 +22,7 @@ import {
   PieChart,
   Sparkles,
 } from 'lucide-react';
+import { GLASS_BLUR } from '@/constants/glassConfig';
 
 /**
  * 建议任务卡片数据
@@ -88,7 +89,7 @@ const SuggestionCard = ({ card, onClick, index }) => {
         w="full"
         p={4}
         bg="rgba(255, 255, 255, 0.03)"
-        backdropFilter="blur(12px)"
+        backdropFilter={GLASS_BLUR.md}
         border="1px solid"
         borderColor="rgba(255, 255, 255, 0.08)"
         borderRadius="xl"