UI: Add Combobox and Autocomplete Status

[mirka]

What?

Adds Combobox.Status and Autocomplete.Status subcomponents that wrap the Base UI Status primitive.

This PR does not add Status to higher-level components such as SearchableChipSelect or SelectControl. Those can take it in a follow-up.

Why?

Autocomplete and Combobox had no way to announce async list status.

How?

Thin wrappers matching Empty.

Tests cover ref forwarding. Keep-mounted live region behavior is Base UI, not something we retest here.

Testing Instructions

1. Open Storybook to Design System / Components / Form / Primitives / Autocomplete / Async Items.
2. Type in the input.
3. Confirm a spinner and "Loading…" appear in the popup, with no options listed, then matching results replace the status.
4. Open Combobox / Async Items.
5. Activate the trigger.
6. Confirm a spinner and "Loading…" appear, then the item list (Apple first).
7. Close and reopen the popup to see the loading state again.
8. In the inspector, confirm the role="status" node stays in the DOM after the message clears.

[github-actions]

Size Change: +59 B (0%)

Total Size: 7.92 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	478 kB	+59 B (+0.01%)

_{compressed-size-action}

[github-actions]

Flaky tests detected in 3f7eca6.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/33426202645
📝 Reported tests:

As a user I want to be able to customize the navigation overlay with styled content in /test/e2e/specs/site-editor/navigation-overlay-template-part.spec.js, passed after 2 failed attempts.

Error: apiRequestContext.fetch: socket hang up
Call log:
  - → GET http://localhost:8889/wp-json/wp/v2/templates
    - user-agent: Playwright/1.62.1 (x64; ubuntu 24.04) node/20.20 CI/1
    - accept: */*
    - accept-encoding: gzip,deflate,br
    - X-WP-Nonce: cb6c48ef31
    - cookie: wordpress_test_cookie=WP%20Cookie%20check; wordpress_logged_in_23778236db82f19306f247e20a353a99=admin%7C1788374887%7CqkXZgeZ2tqDsa4pLXNLG22GYkIN08ZiVvp6x5s3sb4F%7Cbba0b07c257c53a66e6ca43aeeb238f3e977ede30a4425b9e610bd09279e2d1e; wp-settings-time-1=1788203129

    at RequestUtils.rest (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/rest.ts:112:39)
    at RequestUtils.deleteAllTemplates (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/templates.ts:35:31)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/site-editor/navigation-overlay-template-part.spec.js:57:22
TimeoutError: locator.click: Timeout 10000ms exceeded.
Call log:
  - waiting for getByRole('button', { name: 'Create overlay', exact: true })

    at createNavigationOverlay (/home/runner/work/gutenberg/gutenberg/test/e2e/specs/site-editor/navigation-overlay-template-part.spec.js:44:28)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/site-editor/navigation-overlay-template-part.spec.js:113:4

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: mirka <0mirka00@git.wordpress.org>
Co-authored-by: ciampo <mciampini@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[ciampo]

LGTM 🚀

[ciampo]

Should we also check that the rendered node has role="status", aria-live="polite", and aria-atomic="true"? Or do we delegate / trust base ui on this? (the current ref assertion would also pass for a plain <div>, so it does not protect the accessible behavior these subcomponents add)