Replace tailwind directives in editor css

[pkosciak]

When the editor is not using an iframe, some WordPress core styles override Tailwind's styles. This occurs because WordPress's built-in styles (e.g., wp-includes/css/dist/block-library/reset.css) are applied directly to the editor content and are unlayered. In contrast, Tailwind styles are applied using CSS layers. Unlayered styles take precedence over layered ones—even if Tailwind's selectors have higher specificity, they can still be overridden by WordPress’s built-in styles.

To ensure Tailwind styles are not layered (and thus have higher precedence), we can import each Tailwind file individually using import directives. This approach prevents Tailwind from being wrapped in a layer, allowing its styles to override the CMS defaults.

[ehclau]

I tried various approaches for dealing with Wordpress editor styles overriding tailwind and still encountered edge cases here and there. Found a potentially reliable approach:

@import "tailwindcss" important;

Reference:
tailwindlabs/tailwindcss#15803

[retlehs]

Should we solve this with split imports, or use Tailwind v4's @import "tailwindcss" important; for editor CSS? For reference, Radicle's editor.css uses @import "tailwindcss" theme(static);

Sage main currently uses @import "tailwindcss"; in editor.css, so this PR isn't dropping theme(static) relative to Sage. Still, should we consider adopting theme(static) here for parity/consistency? If we keep split imports, a brief note on why this approach was chosen over important would be helpful.