fix(a11y): name badged sidebar items by their visible text and stop phantom contrast failures in a11y scans (#14630)

fix(a11y): sidebar item names include their Beta/Legacy badge; settle animations before IBM scans

- sidebarDraggableComponent: accessible name contains the visible badge
  text (WCAG 2.5.3 Label in Name)
- tests/fixtures runA11yScan: wait for finite animations to finish so
  the IBM checker no longer reports phantom contrast on fading popovers
- baseline the two Radix focus-guard spans on the model-picker scan state
- new spec: model-picker contrast (light/dark) + sidebar label-in-name