Administration: Align border-radius values with design system tokens

[Dervish12]

Summary

Replace non-standard border-radius values across 7 admin CSS files with their nearest equivalents from the WordPress design system defined in _tokens.scss.

Trac ticket: https://core.trac.wordpress.org/ticket/65444

Problem

The WordPress design system (_tokens.scss) defines a clear border-radius scale: 1px, 2px, 4px, 8px, 12px, 9999px. However, several admin CSS files still use legacy values (3px, 5px, 9px, 10px, 11px) that fall outside this scale, creating visual inconsistency.

Changes

Old value	New value	Design token	Locations	Elements
3px	2px	radius-s	10	Buttons, save controls, theme cards, menu items
5px	4px	radius-m	3	Comment count badges, bookmarklet button
9px	8px	radius-l	1	Admin menu notification badges
10px	8px	radius-l	1	Site icon previews
11px	12px	radius-30	1	Pending comment count badge

Files changed

• src/wp-admin/css/themes.css — 5 replacements
• src/wp-admin/css/list-tables.css — 4 replacements
• src/wp-admin/css/customize-controls.css — 3 replacements
• src/wp-admin/css/admin-menu.css — 1 replacement
• src/wp-admin/css/forms.css — 1 replacement
• src/wp-admin/css/nav-menus.css — 1 replacement
• src/wp-admin/css/site-icon.css — 1 replacement

Test plan

• npm run build:dev — builds successfully
• Verify theme browser cards, customizer save button, admin menu badges, comment count badges all render correctly
• Compare against trunk — differences should be 1px or less, barely perceptible

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[github-actions]

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