Hide resizer when wiki sidebar is collapsed

Rinku Crequested to merge
gitlab-community/gitlab-org/gitlab:rc_fix_hide_sidebar_resizer_when_collapsed into master

What does this MR do and why?

Hide resizer when wiki sidebar is collapsed

References

#580565

Screenshots or screen recordings

Before After
Screen Recording 2025-12-11 at 22.21.25.mov Screen Recording 2025-12-11 at 22.21.57.mov

How to set up and validate locally

  1. Checkout this branch and run gdk locally
  2. Go to any project's wiki page, if there isn't any wiki create a new page
  3. Try resizing the sidebar and notice the resizer
  4. Close the sidebar using button near the page title and notice the resizer element being hidden

Merge request reports