"Pending message" doesn't clear on correct timming

### Describe the bug

Found an issue where my Pending message is already consumed and the agent is thinking on it (I can read the thinking) but the message still has "(pending)" appended to it, thus misleading me.

### Affected version

GitHub Copilot CLI 1.0.75.

### Steps to reproduce the behavior

1. Ask tasks that need thinking while on medium or high thinking
2. Add additional prompts while it is still processing (you message is now pending)
3. Check the "Pending message" is appended
4. when the agent start thinking about your message, check the "Pending message" text is still present, although the message has already been delivered.

### Expected behavior

The "pending message" should clear before the agent starts thinking about the message, becaue by now it no longer is pending but was already delivered.

### Additional context

_No response_

在 GitHub Copilot CLI 1.0.75 中，通过在中等或高强度思考期间发送一个排队中的提示来复现此问题，然后在 agent 开始处理该提示时观察它。跟踪待处理消息显示从 queued 转换为 delivered 的过程，并在 agent 开始思考该消息之前“(pending)”文本消失时，认为该 issue 已完成。

由索引模型根据 Issue 内容生成。