产品方向讨论：PR #2002 侧栏任务时间显示设置

本 PR 新增侧栏设置项控制任务相对时间显示/隐藏，改动涉及外观设置、会话卡片与会话列表项组件。

改动范围：
- apps/desktop/src/renderer/components/settings/AppearanceSection.tsx
- apps/desktop/src/renderer/features/cc-agent/sidebar/SessionCard.tsx
- apps/desktop/src/renderer/features/cc-agent/sidebar/SessionItem.tsx

维护者在 PR 上 Approve 即放行；需要修改请 Request Changes，作者改完后重新 Approve 即可。

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关联 PR:#2002(作者 @jiangtianqi-xd);本 issue 由 review-pr 流程自动创建,用于先讨论该 PR 涉及的产品 / UI 变更,维护者确认后 PR 会恢复推进。

Review PR #2002 and the three named files: AppearanceSection.tsx, SessionCard.tsx, and SessionItem.tsx. Start by examining the proposed appearance setting and how it affects relative task times in the sidebar. Done means the product decision is confirmed and PR #2002 can proceed or be revised accordingly.

Written by the indexing model from the issue text.