[Feature Request]I would like to see conversation history title generation switched to Nova Lite

## Describe the solution you'd like

If your region supports it, please switch conversation history title generation to Nova Lite.

## Why the solution needed

Because Nova Lite is faster and less expensive.

## 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.

No files, tests, or entry points are named. Start by locating conversation history title generation and the model-selection configuration, then verify regional support and confirm titles use Nova Lite where supported.

Written by the indexing model from the issue text.