[EuiSelectable][A11y] Search input is not read out by screen readers

[jorgeoliveira117]

Closes #9161

Summary

Updates focus behavior in EuiSelectable and ARIA attributes to match best practices. When focusing the search input, the active option remains visually focused, and aria-activedescendant is only added when an option is active.

Why are we making this change?

• To preserve focus: Moving focus between the search input and the item list should keep the active option visually focused, improving keyboard navigation.

• ARIA compliance: aria-activedescendant should only be present when there is an active descendant. An empty string is invalid.

Screenshots

Before:
When we open the popover/dialog and focus inside the Selectable component, the first item on the list is also focused

Before.mp4

After:
When we focus inside the Selectable component, now the first item isn't focused, only the search input

After.mp4

Impact to users

🟢 No breaking changes. No code updates are required on consumer side.

ℹ️ This fix has been run in Kibana CI and required test changes have been prepared here.

✨ User value

• Better keyboard navigation as active option remains visible when focusing the search input
• Improved accessibility as ARIA attributes follow best practices
• More consistent UX when switching between search and list

QA

General checklist

• Browser QA
  • Checked in both MacOS and Windows high contrast modes
    • (emulate forced colors if you do not have access to a Windows machine.)
  • Checked in mobile
  • Checked in Chrome, Safari, Edge, and Firefox
  • Checked for accessibility including keyboard-only and screenreader modes
• Code quality checklist
  • Added or updated jest and cypress tests
• Release checklist
  • A changelog entry exists and is marked appropriately
  • If the changes unblock an issue in a different repo, smoke tested carefully (see Testing EUI features in Kibana ahead of time)

[mgadewoll]

Thanks for picking up this A11y fix!
I left a couple small comments for improvements, but in general the proposed update works as expected (tested in Jaws, NVDA and VoiceOver). 🎉

⚠️ Let's make sure to run the changes in Kibana CI and wait for the results to understand what might break and if there is anything else we might need to address.

[mgadewoll]

ℹ️ @jorgeoliveira117 I merged main into your branch to have it updated before merging.
I also confirmed that the latest run of these changes on Kibana CI looked clean 👍

[mgadewoll]

🟢 The changes work as expected and fix the A11y issue.
Thank you for contributing! 🎉

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: b5de3ca
• Documentation website
• Storybook

History

• 💚 Build #2040 succeeded f865f0c
• 💔 Build #2038 failed dcdfa9c
• 💚 Build #2033 succeeded 2b4af79
• 💚 Build #2030 succeeded 2ce4f0d
• 💚 Build #2006 succeeded 750cbde
• 💚 Build #2003 succeeded 70a556e

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: b5de3ca

History

• 💚 Build #5297 succeeded f865f0c
• 💔 Build #5296 failed dcdfa9c
• 💚 Build #5293 succeeded 2b4af79
• 💚 Build #5290 succeeded 2ce4f0d
• 💚 Build #5285 succeeded 10eca7e
• 💚 Build #5269 succeeded 750cbde