Add /restart command

[krubenok]

Describe the feature or problem you'd like to solve

After an update is available, it tells me to restart to apply it - I can of course /exit then copilot to do that, but it would be nice to just /restart

Proposed solution

/restart command that applies pending updates and returns back to the same spot I was in.

Example prompts or workflows

No response

Additional context

[examon]

This was added in v1.0.3. The /restart slash command restarts the CLI in place while preserving your current session, and /update also uses it to automatically restart after applying updates. If you're still not seeing that behavior, feel free to reopen this issue.