I’m seeing a model entitlement mismatch in Copilot CLI.

### Describe the bug

The same GitHub account can use Claude models in VS Code and on GitHub.com, but in Copilot CLI `/model` shows Claude models only
under `Upgrade` with the message: “Your subscription does not include these models.”

### Affected version

GitHub Copilot CLI 1.0.12

### Steps to reproduce the behavior

 1. Open Copilot CLI
2. Run `/model`
3. `Available` only shows GPT models
4. Switch to `Upgrade` and Claude models appear there
5. `--model claude-sonnet-4.5` returns: `Model "claude-sonnet-4.5" from --model flag is not available.

I reproduced this again after a fresh isolated login using a new config directory, so this does not appear to be caused by local
cache or stale login state.

### Expected behavior

Claude models should be available in Copilot CLI as they are for the same account in VS Code and on GitHub.com.

### Additional context

 Environment:
- GitHub Copilot CLI 1.0.12
- Windows 11
- Windows Terminal

Start by reproducing the issue in Copilot CLI 1.0.12 with `/model` and `--model claude-sonnet-4.5`, using a fresh isolated login and configuration directory. Trace how the CLI determines subscription model availability and compare that result with the account's access in VS Code and on GitHub.com; done means Claude models appear under Available and the flag succeeds.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.