Storing sessions in a repository

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

Currently sessions are only stored on the local computer and hard to share

### Proposed solution

Working with copilot-cli on a repository often produces valuable state / results in the session directories but its often a bit hard to keep track of those and they can easily pile up when working on many different ones.

As a "session" is just a collection of files, I wonder if one would be able to have something like a `.copilot` folder in a repository where the sessions can be stored. This would allow to even commit / share the session and reuse it e.g. on another computer or with a different user.

### Example prompts or workflows

_No response_

### Additional context

_No response_