Fix wiki sidebar vertical scroll

What does this MR do and why?

This MR pushes a fix for long wiki sidebars not being able to scroll while the parent container is not scrolled to its end.

References

Screenshots or screen recordings

Before	After
Screen_Recording_2025-10-21_at_06.25.44 (Scrolling with the page only)	Screen_Recording_2025-10-21_at_06.18.47 (scrolling independently of the page)

How to set up and validate locally

1. Open a Wiki and create so many pages that the wiki sidebar has more entries than fit in your viewport.
2. scroll the sidebar.
3. enable the new UI (or old UI) (you may need to run Feature.enable(:paneled_view))
4. check again.

MR acceptance checklist

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