The Ubuntu dock shows a notification badge for the Copilot app, but there’s n...

The Ubuntu dock shows a notification badge for the Copilot app, but there’s no clear way inside the app to see what triggered it. Please add an in-app notification/activity center with unread items and links to the relevant session.

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| Field | Value |
| --- | --- |
| App version | 1.1.0 |
| OS | Ubuntu 24.4.0 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Day 2 (Week 1) |

从 /chat 路径开始，在应用版本 1.1.0 中复现 Ubuntu dock badge。追踪 Copilot 应用如何显示该 badge，并检查现有的会话导航。完成的标准是：应用内活动中心会显示未读项目，并链接到相关会话，使用户能够在应用内理解 badge 状态。

由索引模型根据 Issue 内容生成。