refactor(agent): 重构智能体页面布局和样式

-调整了智能体卡片的布局结构，优化了标题和描述的显示方式
- 改进了历史对话的展示样式，增加了滚动指示器
- 统一了标签和图标的样式，提升了视觉一致性
- 优化了搜索框和卡片列表的样式，提高了用户体验

src/assets/svg/menu-fold.svg

@@ -0,0 +1,3 @@
+<svg width="20" height="20" viewBox="0 0 20 20" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M17.5 5.41667H2.5V3.75H17.5V5.41667ZM17.5 10.8333L9.16667 10.8333V9.16667L17.5 9.16667V10.8333ZM2.5 16.25L17.5 16.25V14.5833L2.5 14.5833V16.25ZM5.88166 7.49938C6.1589 7.31999 6.52469 7.51898 6.52469 7.8492V11.9793C6.52469 12.3095 6.1589 12.5085 5.88167 12.3291L2.69031 10.264C2.43656 10.0999 2.43656 9.7286 2.69031 9.5644L5.88166 7.49938Z" fill="#737478"/>
+</svg>

src/assets/svg/menu-unfold.svg

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+<svg width="20" height="20" viewBox="0 0 20 20" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M2.5 5.41667H17.5V3.75H2.5V5.41667ZM9.16667 10.8333L17.5 10.8333V9.16667L9.16667 9.16667V10.8333ZM17.5 16.25L2.5 16.25V14.5833L17.5 14.5833V16.25ZM2.5 7.93499C2.5 7.60478 2.86579 7.40578 3.14302 7.58517L6.33438 9.6502C6.58813 9.81439 6.58812 10.1856 6.33438 10.3498L3.14302 12.4149C2.86579 12.5943 2.5 12.3953 2.5 12.065V7.93499Z" fill="#737478"/>
+</svg>