feat: add React Compiler support for Heading, Link, Pagehead, Portal, and SideNav

[joshblack]

Closes N/A

Changelog

New

N/A

Changed

• Enabled React Compiler support for Heading, Link, Pagehead, Portal, and SideNav.
• Added a patch changeset for the rendering performance improvement.

Removed

N/A

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

Testing & Reviewing

• npx eslint --no-cache packages/react/src/Heading/**/*.{ts,tsx} packages/react/src/Link/**/*.{ts,tsx} packages/react/src/Pagehead/**/*.{ts,tsx} packages/react/src/Portal/**/*.{ts,tsx} packages/react/src/SideNav.tsx packages/react/src/__tests__/SideNav*.tsx
• npm test -- --run packages/react/src/Heading packages/react/src/Link packages/react/src/Pagehead packages/react/src/Portal packages/react/src/__tests__/SideNav.test.tsx packages/react/src/__tests__/SideNav.types.test.tsx
• npm run build && npm test -- --run && npm run type-check && npm run lint && npm run lint:css && npm run format:diff
• Storybook started and responded locally at http://localhost:6006.

Merge checklist

• Added/updated tests (not needed; existing coverage validated)
• Added/updated documentation (not needed)
• Added/updated previews (not needed)
• 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-ui (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 59aa20d

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

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

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]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. If this doesn't work, you can also use the original workflow here. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

To publish a canary release for integration testing, apply the Canary Release label to this PR.

[Copilot]

Pull request overview

Enables React Compiler support for additional @primer/react components by removing them from the opt-out list, and records the user-visible performance improvement via a patch changeset.

Changes:

• Removed Heading, Link, Pagehead, Portal, and SideNav from the React Compiler “unsupported” ignore patterns.
• Added a patch changeset describing the resulting rendering performance improvement.

Show a summary per file

File	Description
packages/react/script/react-compiler.mjs	Updates the React Compiler exclusion list to allow compilation for Heading/Link/Pagehead/Portal/SideNav.
.changeset/react-compiler-primitives.md	Adds a patch changeset entry for the performance improvement.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1

[primer-integration]

Integration test results from github/github-ui PR:

  CI Failed
  VRT Running
  Projects Waiting

CI check runs linting, type checking, and unit tests. Check the workflow logs for specific failures.

Need help? If you believe this failure is unrelated to your changes, please reach out to the Primer team for assistance.