Update Docs to use React v19

[danielguillan]

Summary

Towards https://github.com/github/primer/issues/6134. Updates React, NextJS, Doctocat, and Primer React to latest versions in docs.

List of notable changes:

• Upgrade @primer/doctocat-nextjs from 0.7.0 to 0.8.0
• Upgrade @primer/react from 37.11.2 to 38.6.1
• Upgrade next from 15.5.2 to 15.5.9
• Update React version constraints to support React 18 and 19
• Remove styled-components dependency (no longer required by @primer/react 38.x)
• Remove motion-dom override (no longer needed)
• Refactor color-scales components to use CSS modules instead of @primer/react Box with sx prop

What should reviewers focus on?

• Review updated docs
• Ensure Color primitives page works as expected

Supporting resources (related issues, external links, etc):

• https://github.com/github/primer/issues/6134
• Doctocat v0.8.0

[changeset-bot]

⚠️ No Changeset found

Latest commit: a845027

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[github-actions]

🟢 No design token changes found

[github-actions]

🟢 No visual differences found

Our visual comparison tests did not find any differences in the UI.

[Copilot]

Pull request overview

This PR updates the next-docs app to support React 19 by upgrading React, Next.js, Doctocat, and Primer React to their latest versions. The major change involves removing the styled-components dependency and refactoring color-scale components to use CSS modules instead of the @primer/react Box component with sx prop.

Key changes:

• Upgraded React from 18.x to 19.x support (>=18 <= 19)
• Upgraded @primer/react from 37.11.2 to 38.6.1 (which no longer requires styled-components)
• Refactored ColorThemePicker and ColorScales components to use CSS modules

Reviewed changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
apps/next-docs/package.json	Updated dependency versions for React 19, Next.js 15.5.9, @primer/react 38.6.1, @primer/doctocat-nextjs 0.8.0; removed styled-components and motion-dom override
apps/next-docs/package-lock.json	Lockfile updates reflecting dependency changes and transitive dependency updates
apps/next-docs/src/components/color-scales/ColorThemePicker.js	Refactored from @primer/react Box/sx to native HTML elements with CSS module classes
apps/next-docs/src/components/color-scales/ColorScales.js	Refactored from @primer/react Box/sx to native div elements with CSS module classes
apps/next-docs/src/components/color-scales/ColorScales.module.css	New CSS module file containing styles previously defined via styled-system sx prop
apps/next-docs/content/components/Label/index.mdx	Removed unused @primer/react Box import

[rezrah]

LGTM 🚀

[rezrah]

@danielguillan i just remembered that we can now start hoisting the dependencies again in the root:

https://github.com/primer/brand/blob/main/package.json#L26

So you can remove this line, and run npm i again, it'll bring apps/next-docs deps back to the root node_modules.