Reduce duplicated preset utility implementations

[scruffian]

What?

Reduces duplicated preset utility implementations in the block editor spacing and border radius controls.

Why?

Spacing and border radius controls had overlapping helper logic for identifying preset values, extracting preset slugs, and resolving preset values. Keeping that logic centralized makes future preset behavior changes less likely to drift between controls.

How?

• Updates spacing helpers to reuse the generic preset-input utilities for preset detection and slug extraction while preserving the public isValueSpacingPreset export for backwards compatibility.
• Updates border radius preset conversion to reuse the generic preset-input utilities instead of maintaining border-radius-specific copies.
• Removes now-redundant border radius utility tests that are covered by the generic preset-input utility tests.

Testing Instructions

Run npm run test:unit -- packages/block-editor/src/components/spacing-sizes-control/test/utils.js packages/block-editor/src/components/border-radius-control/test/utils.js packages/block-editor/src/components/preset-input-control/test/utils.js.

Testing Instructions for Keyboard

No keyboard-specific testing is needed because this refactors shared helper implementations without changing UI behavior.

Screenshots or screencast

Not applicable.

Use of AI Tools

This PR was authored with assistance from OpenAI Codex in Conductor; the generated changes were reviewed before submission.

[github-actions]

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Co-authored-by: jeryj <jeryj@git.wordpress.org>

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[github-actions]

Size Change: +33 B (0%)

Total Size: 7.72 MB

📦 View Changed

Filename	Size	Change
build/modules/content-types/index.min.js	164 kB	-11 B (-0.01%)
build/scripts/block-editor/index.min.js	421 kB	+44 B (+0.01%)

_{compressed-size-action}

[github-actions]

Flaky tests detected in 261d827.
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/29420557510
📝 Reported issues:

• [Flaky Test] does not dirty related template parts or navigation menus when rendered in the post editor #79294 in /test/e2e/specs/editor/blocks/navigation-passive-rendering.spec.js
• [Flaky Test] should allow user to add and remove multiple local font files #78760 in /test/e2e/specs/admin/font-library.spec.js
• [Flaky Test] should undo typing after non input change #78702 in /test/e2e/specs/editor/various/undo.spec.js
• [Flaky Test] shows disabled blocks in list view and constrains keyboard navigation #80042 in /test/e2e/specs/editor/various/list-view-spotlight-mode.spec.js

[jeryj]

Functionally looks good. Approving but I think we should remove the getPresetSlug test.

[jeryj]

Haven't looked yet, but I assume these tests already exist within getPresetSlug from preset-input-control? I think we could just get rid of these tests if they are tested within preset-input-control.

[jeryj]

If isValuePreset( value, SPACING_PRESET_TYPE ) handles it, maybe we use that instead? Or is isvalueSpacingPreset publicly exported?

[jeryj]

Ah, it is publicly exported. Nevermind.