/ask mode

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

Ask a question to LLM without editing the code

### Proposed solution

It looks like Copilot is always in Agent mode. Even if you ask a question, he will make edits or run terminal commands.

It would be nice if there is /ask command that just make it answer the question like with normal chat. So you don't need to leave the tool just to ask a question to the LLM.

### Example prompts or workflows

I asked:

> Do you need to need to ignore all workspaces inside git? This repository has base
> directory that is base branch. The branch is suppose to have just the base
> project, like a template on GitHub, that later may be pushed into different
> repository.

He ran some checks and edited the `.gitignore` file and ignored the base work tree

I mistakenly asked about workspaces instead of work trees. But this is just a minor detail.

I just wanted to ask a question. I didn't expect agent to edit the code.

### Additional context

_No response_