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

Start by reproducing the issue through `/rename` and `/resume`, then trace where manual names and later auto-generated session names are handled. The work is done when a name set with `/rename` remains unchanged across continued work and still appears under that name in `/resume` until explicitly renamed again.

Written by the indexing model from the issue text.