UI: Add Autocomplete.Row primitive

[mirka]

What?

Adds the missing Autocomplete.Row primitive to @wordpress/ui and documents it with an inline grid Storybook example.

Why?

Base UI's Autocomplete supports grid layouts via Autocomplete.Row, but the WordPress UI wrapper did not expose this part yet. Exporting it unlocks multi-cell rows in grid-mode autocomplete lists, such as emoji pickers.

How?

Add a thin Row wrapper around Base UI's Autocomplete.Row.

Testing Instructions

1. Run Storybook for @wordpress/ui.
2. Open Design System / Components / Form / Primitives / Autocomplete.
3. See the Grid story.

Screenshots

[github-actions]

Size Change: 0 B

Total Size: 7.74 MB

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[github-actions]

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[github-actions]

Flaky tests detected in a41865b.
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/29773622904
📝 Reported issues:

• [Flaky Test] Should navigate inner blocks with arrow keys #39607 in /test/e2e/specs/editor/various/writing-flow.spec.js