Copilot CLI screen goes blank when using /new to start a new session

### Describe the bug

Copilot CLI screen goes blank when using /new to start a new session with an already running session currently being worked on

### Affected version

1.0.67

### Steps to reproduce the behavior

1. This happens intermittently but often enough to get bothersome
2. Usual scenario that I've noticed, I have a long running session which is running, and I want to start a new session with /new
3. The /new makes the CLI screen blank with no escape back to the previous session
4. The only way I've been able to get out of this situation is to kill the process and start CLI over again

### Expected behavior

Ability to create a new session and work across sessions while the previous session continues in the background

### Additional context

_No response_

未指定檔案或測試。先在另一個工作階段正在執行時，使用 CLI /new 命令重現間歇性空白畫面，然後追蹤工作階段切換的進入點。完成條件是 /new 建立可用的新工作階段，同時先前的工作階段在背景繼續執行，且不需要終止程序。

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