Not asking for approval in plan mode

### Describe the bug

I noticed that after it had just come out of auto-pilot mode, after implementing a previous plan, if I was to go into plan mode again, it seemed that it didn't want to ask me for approval of a plan before implementing the changes.

### Affected version

GitHub Copilot CLI 1.0.22

### Steps to reproduce the behavior

1. In plan mode, write an implementation plan for something.
2. After the plan is presented, press "Implement with Autopilot" or "Continue on Autopilot", whatever the option is.
3. After the plan is implemented in Autopilot, shift tab to go back to plan mode.
4. Ask it a follow-up, expecting a new plan.

### Expected behavior

I would still expect this to output a plan and ask me for approval.

### Additional context

I've only noticed this in this current version and the one immediately previous. It may have been there beforehand; I just hadn't noticed it.

按照 plan-mode 和 Autopilot 的轉換步驟，在 GitHub Copilot CLI 1.0.22 中重現此問題。先追蹤從 Autopilot 返回 plan mode 的轉換，然後驗證後續請求會產生計畫，並在實作前請求核准。

由索引模型根據 Issue 內容生成。