Manual `/rename` is overwritten by later auto-generated session name

### Describe the bug

A session name set manually via `/rename ` does not persist reliably. After continuing to work in the same session, Copilot CLI auto-renames the session again and overwrites the user-defined name.

### Affected version

GitHub Copilot CLI 1.0.22

### Steps to reproduce the behavior

1. Start a new Copilot CLI session.
2. Run `/rename my-name`.
3. Continue working in the same session for a while.
4. Check the session name again, or try to find it later in `/resume`.

### Expected behavior

A manually assigned session name should remain unchanged until the user explicitly renames it again.

### Additional context

- Actual behavior: the manual name is replaced by an automatically generated session name.
- Impact: renamed sessions become hard to find later because the expected custom name no longer exists.
- OS: Windows
- Terminal: Windows Terminal
- Shell: PowerShell

先透過 `/rename` 和 `/resume` 重現問題，接著追蹤手動設定的名稱以及之後自動產生的工作階段名稱是在哪裡處理的。當使用 `/rename` 設定的名稱在繼續工作期間保持不變，並且在再次明確重新命名之前始終以該名稱出現在 `/resume` 中時，工作就完成了。

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