'!Failed to load N skills' error even though all skills are disabled.

### Describe the bug

I have disabled all skills. When I open a new copilot session from Windows Terminal, I see '!Failed to load N skills' error even though all skills are disabled.

### Affected version

GitHub Copilot CLI v1.0.67

### Steps to reproduce the behavior

1. Type copilot in Windows Terminal
2. Press Enter
3. Disable all skills
4. Exit copilot
5. Type copilot
6. Press Enter
7. View error message

### Expected behavior

Zero error messages appear when starting a copilot session from Windows Terminal with all skills disabled.

### Additional context

_No response_

首先，从 Windows Terminal 中的 Copilot 入口点复现该问题：禁用所有 skills，退出，然后启动一个新会话。跟踪对“!Failed to load N skills”消息的启动处理，并验证在禁用每个 skill 的情况下重新启动不会产生任何错误消息。

由索引模型根据 Issue 内容生成。