👐 a11y: Improve Fork and SplitText Accessibility (#7147)

* refactor: Replace Popover with Ariakit components for improved accessibility and UX

* wip: first pass, fork a11y

* feat(i18n): Add localization for fork options and related UI elements

* fix: Ensure Dropdown component has correct z-index for proper layering

* style: Update Fork PopoverButton styles and remove unused sideOffset prop

* style: Update text colors and spacing in Fork component for improved readability

* style: Enhance Fork component's UI by adding select-none class to prevent text selection

* chore: Remove unused Checkbox import from Fork component

* fix: Add sr-only span for accessibility in SplitText component

* chore: Reorder imports in Fork component for better organization

client/src/components/Nav/SettingsTabs/Chat/ForkSettings.tsx

@@ -44,6 +44,7 @@ export const ForkSettings = () => {
               options={forkOptions}
               sizeClasses="w-[200px]"
               testId="fork-setting-dropdown"
+              className="z-[50]"
             />
           </div>
         </div>