Adjust wider size for the source pdf box (which worked in the previous version)

Thanks for fixing the issue of not able to hide the chat box in the new version.

However, in the track mode, it would be much better if the source pdf viewer box can allow us to adjust in a wider range, which worked in the previous version, so users can look at the source pdf clearly (especially you know in the 10.1’ iPad), while we can read the notes from AI Professor and response to AI Professor (via typing box)