Cannot add directory to allow list because of special character in path

### Describe the bug

My company had a comma in their OneDrive name. When I try to add the path to the dir it fails because of this. They will not change it.

### Affected version

GitHub Copilot CLI 1.0.12

### Steps to reproduce the behavior

1. Try to run /add-dir where the path has a special character, such as a comma.

### Expected behavior

Should fail to add the dir to allow list.

### Additional context

_No response_

Start at the CLI entry point for /add-dir and reproduce the failure using a path containing a comma, such as the reported OneDrive path. Clarify the expected behavior, then add coverage for the special-character path and verify that the allow-list operation matches the agreed behavior.

Written by the indexing model from the issue text.