UI: Align Calendar styling with WPDS tokens

[ciampo]

Follow up to #81337.

Related discussions:

• UI: Add Calendar and RangeCalendar, moved from components private APIs #81337 (comment)
• UI: Add Calendar and RangeCalendar, moved from components private APIs #81337 (comment)

What?

Aligns Calendar and RangeCalendar day states with the neutral interactive WPDS token family.

Why?

Calendar day buttons mixed content and interactive tokens, and switched from neutral to brand tokens between states. The range fill and preview also derived colors with color-mix() instead of using semantic WPDS tokens directly.

How?

Unselected days now follow the neutral minimal Button state model. Selected endpoints keep the existing neutral strong treatment. Range middles use the neutral weak active background, and range previews use the neutral interactive stroke token.

Testing Instructions

1. Open Storybook → Design System/Components/Calendar.
2. Hover and select days. Confirm unselected days use a subtle neutral background and selected days retain the strong neutral treatment.
3. Open Storybook → Design System/Components/RangeCalendar.
4. Select and preview a range. Confirm the middle fill and dashed preview use neutral colors.
5. Repeat with the WordPress global CSS toggle and forced-colors emulation. Confirm the states remain visible.

Testing Instructions for Keyboard

1. Focus a day in each Calendar story.
2. Move through days with the arrow keys and select with Enter or Space.
3. Confirm the focused day keeps a visible focus ring and the neutral active background.

Use of AI Tools

OpenAI Codex was used to inspect the follow-up discussions, implement the CSS changes, run validation, and draft this description.

[github-actions]

Size Change: -354 B (0%)

Total Size: 7.71 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	459 kB	-9 B (0%)
build/scripts/edit-site/index.min.js	334 kB	-11 B (0%)
build/scripts/editor/index.min.js	530 kB	-17 B (0%)
build/scripts/media-utils/index.min.js	154 kB	-24 B (-0.02%)
build/styles/block-library/navigation-overlay-close/style-rtl.css	260 B	-64 B (-19.75%)	🎉
build/styles/block-library/navigation-overlay-close/style-rtl.min.css	239 B	-61 B (-20.33%)	🎉
build/styles/block-library/navigation-overlay-close/style.css	260 B	-64 B (-19.75%)	🎉
build/styles/block-library/navigation-overlay-close/style.min.css	239 B	-61 B (-20.33%)	🎉
build/styles/block-library/style-rtl.css	22.4 kB	-11 B (-0.05%)
build/styles/block-library/style-rtl.min.css	18.9 kB	-11 B (-0.06%)
build/styles/block-library/style.css	22.5 kB	-10 B (-0.04%)
build/styles/block-library/style.min.css	18.9 kB	-11 B (-0.06%)

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