[Feature Request]Ability to close the sidebar

## Describe the solution you'd like

I would like the ability to adjust the margin by closing the sidebar.

## Why the solution needed

We hope that the bot's answers will be easier to see.

## Additional context

Add any other context or screenshots about the feature request here.

## Implementation feasibility

Are you willing to collaborate with us to discuss the solution, decide on the approach, and assist with the implementation?

- [ ] Yes, I am able to implement the feature and create a pull request.
- [x] No, I am unable to implement the feature, but I am open to discussing the solution.

The issue does not name a file or test. Start by locating the sidebar in the TypeScript/React frontend and trace how its layout margin is set. Done means the sidebar can be closed and the bot's answers have more usable horizontal space.

Written by the indexing model from the issue text.