Remove sx support from SplitPageLayout component

[llastflowers]

Closes https://github.com/github/primer/issues/4829

Changelog

Removed

Removed anything associated with styled-components/sx from SplitPageLayout including any references in docs and tests

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

There is currently no sx usage with this component in dotcom, and this will be confirmed again before merging.

Testing & Reviewing

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 94b2f8e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@primer/react	Major
@primer/mcp	Patch
@primer/styled-react	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	90.28 KB (0%)
packages/react/dist/browser.umd.js	90.45 KB (0%)

[primer-integration]

👋 Hi from github/github! Your integration PR is ready: https://github.com/github/github/pull/396923

[primer-integration]

🟢 golden-jobs completed with status success.

[Copilot]

Pull Request Overview

This PR removes styled-components/sx support from the SplitPageLayout component as part of a migration away from styled-components. The change eliminates sx prop support from the main component and all its subcomponents.

• Removes SxProp interface usage from SplitPageLayoutProps type definition
• Updates component documentation to remove deprecated sx prop references
• Removes sx usage from Storybook stories

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/react/src/SplitPageLayout/SplitPageLayout.tsx	Removes SxProp import and sx support from main component type
packages/react/src/SplitPageLayout/SplitPageLayout.stories.tsx	Removes sx prop usage from Storybook template
packages/react/src/SplitPageLayout/SplitPageLayout.docs.json	Removes sx prop documentation from all subcomponents
.changeset/young-timers-accept.md	Adds changeset entry for major version bump

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