Sidebar section sizing

Problem:

Currently, sections in the sidebar (e.g. Folders, Views, Tabs) have fixed or rigid sizing. This limits visibility and usability — especially when one section has many items and another has none.

Proposed Solution:

Make sidebar sections dynamically resizable, similar to how tab columns behave:

• Sections expand when they contain many items

• Collapse or shrink when empty or less active

• Optional: allow manual resizing via drag handles between sections