Stop CSS transition on the Rapid Diffs file toggle button

Stanislav Lashmanovrequested to merge
slashmanov/rapid-diffs-stop-expand-button-transition into master

What does this MR do and why?

This MR removes secondary transition when toggling files in Rapid Diffs. The secondary transition is caused by the fact that there are two buttons: one for collapse, one for expand. Each time a button is clicked it is immediately hidden and another button is shown and focused. That focus activation triggers another transition, which should not be there.

Screenshots or screen recordings

Before After
Screen_Recording_2025-04-30_at_00.50.41 Screen_Recording_2025-04-30_at_00.48.15

How to set up and validate locally

  1. Enable rapid_diffs and rapid_diffs_on_mr_show feature flags
  2. Go to any merge request
  3. Select 'Changes' tab
  4. Add ?rapid_diffs=true to the URL, follow it
  5. Toggle any file
  6. Observe no additional transitions after first click

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