Leaving Canvas Panel Open, Close App (runs in BG), App won't Reopen

### Short summary

Leaving a canvas extension panel open, then closing the app; but leaving it running in the background, results in the app unable to reopen. Quitting the app or ending the background task is the only way to reopen.

### Affected version or release

v1.1.10

### Installation context

Installed from github.com at https://github.com/features/ai/github-app

### What happened?

Using several downloaded and installed, along with several locally installed canvas extension I found that:

- In settings, if "Keep open when window is closed" is toggled on and a canvas extension panel is open on close, then the app will not reopen
- Quitting the app is the only way to reopen it
- When the canvas panel is closed, and in the same conversation (*or any window without a running canvas extension panel open*) then close the app again, then it is able to reopen

### Steps to reproduce

1. Ensure that "Keep open when window is closed" is toggled on
2. Start a conversation, and start a canvas extension
3. Leave the canvas extension panel open
4. Close the app
5. App will not reopen
- Tried on 2 Windows 11 OS

### Expected behavior

The app to open.

### Additional context

_No response_

在启用 "Keep open when window is closed" 的 Windows 11 上进行复现，保持一个会话处于活动状态，并在关闭应用前让 canvas 扩展面板保持打开。首先跟踪应用的后台生命周期和 canvas 面板的关闭行为；当应用能够正常重新打开，且不会退出或结束其后台任务时，即表示完成。

由索引模型根据 Issue 内容生成。