Command line switch to enable limited "kiosk" mode

### Describe the feature or problem you'd like to solve

Add a command-line switch to disable all non-chat function (login, logout, model switching)

### Proposed solution

I've exposed Copilot CLI for the other user with GH_TOKEN to provide a simple read-only Q/A system on the text corpus of documentation.

I really want to disable all non-chat "slash" functions in Copilot CLI and allow only chat-control functions. So the user could only ask questions and could not change anything like the used model and other settings

### Example prompts or workflows

_No response_

### Additional context

_No response_