What

Refactors the admin-ui Page and Header components to use @wordpress/theme design tokens and the Stack component from @wordpress/ui.

Why

The Page component relied on experimental @wordpress/components abstractions (__experimentalHeading, __experimentalHStack, __experimentalVStack) and Sass variables from @wordpress/base-styles. Migrating to @wordpress/theme tokens and the Stack layout primitive aligns this component with the design system's token-based approach, making it easier to maintain and ensuring it benefits from theme-level features.

How

• header.tsx: Replaced Heading with a plain <h2> styled via a new CSS class. Replaced all HStack and VStack instances with Stack from @wordpress/ui — the outer VStack uses render={ <header /> } to preserve the semantic <header> element while leveraging Stack's layout.
• style.scss: Removed all @wordpress/base-styles Sass imports and replaced every variable/mixin usage with --wpds-* CSS custom properties (colors, spacing, typography, borders). Added a new .admin-ui-page__header-title rule with heading font tokens and text truncation.
• package.json: Added @wordpress/ui as a dependency.

Token mapping

Testing

• Enable the Extensible Site Editor experiment and navigate to Appearance -> Editor
• Check for any visual regressions

Screenshots

Before	After