Compose: Fix useFocusOnMount falling back too early when input controls load asynchronously

[Mustafabharmal]

What?

Fixes useFocusOnMount (firstInputElement mode) incorrectly focusing the close button on first open of the DataViews quick edit Author field.

Closes #75540.

Why?

useFocusOnMount tried to find an input element in a single setTimeout(..., 0). Async DataViews controls (e.g. Author select) render a <Spinner /> while fetching, replacing it with <select> only after the API response arrives. The hook fired before that happened and immediately fell back to the first tabbable element, the close button.

How?

When in firstInputElement mode and no input is found, the hook now retries every 50ms up to 4 times (~200ms total). If the input appears within that window it gets focused; otherwise it falls back to the existing behaviour (first tabbable element).

Testing Instructions

1. Enable "Data Views: add Quick Edit" from Gutenberg Experiments
2. Visit Site Editor → Pages (table or grid layout)
3. Open the quick edit dialog
4. Click the "Author" field
5. The select element should receive focus (not the close button)
6. Subsequent openings should also focus the select correctly

Screenshots or screencast

Before:

Before.Fix.mov

After:

After.Fix.mov

[github-actions]

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Co-authored-by: Mustafabharmal <mustafabharmal@git.wordpress.org>
Co-authored-by: nirav7707 <niravsherasiya7707@git.wordpress.org>
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[github-actions]

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[nirav7707]

@Mustafabharmal Good approach, but I’d recommend using the state to reinitialize the element focus instead of relying on setTimeout and a four-iteration checking loop.