Improve organization of background tasks and artifacts

## Problem

Background tasks and artifacts become difficult to manage as their number grows. The current lists do not provide enough ways to find or organize older items.

## Proposed improvements

- Sort or group items by creation time
- Group items by date or session
- Pin important artifacts
- Add labels or color coding for easier identification

These controls should make large task and artifact lists easier to scan and manage.

首先检查应用中当前的后台任务和 artifact 列表体验。明确范围内的组织能力是排序、分组、固定还是 labels，并定义用户如何找到较旧的项目，以及如何识别工作已完成。issue 中没有指定文件、入口点或测试。

由索引模型根据 Issue 内容生成。