Restore missing control tokens in ESM mode

[rezrah]

Summary

Resolves #1424

Control tokens via functional/size.css weren't added to the global side-effect list, even though they are used across a number of components. This fixes that.

List of notable changes:

• Adds functional control tokens to the global side effect list
• Adds a test for CI

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

Contributor checklist:

• All new and existing CI checks pass
• Tests prove that the feature works and covers both happy and unhappy paths
• Any drop in coverage, breaking changes or regressions have been documented above
• UI Changes contain new visual snapshots (generated by adding update snapshots label to the PR)
• All developer debugging and non-functional logging has been removed
• Related issues have been referenced in the PR description

Reviewer checklist:

• Check that pull request and proposed changes adhere to our contribution guidelines and code of conduct
• Check that tests prove the feature works and covers both happy and unhappy paths
• Check that there aren't other open Pull Requests for the same update/change

Screenshots:

Please try to provide before and after screenshots or videos

Before	After

[changeset-bot]

🦋 Changeset detected

Latest commit: bb31026

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

This PR includes changesets to release 9 packages

Name	Type
@primer/react-brand	Patch
@primer/brand-docs	Patch
@primer/brand-css	Patch
@primer/brand-primitives	Patch
@primer/brand-e2e	Patch
@primer/brand-fonts	Patch
@primer/brand-mcp	Patch
@primer/brand-config	Patch
@primer/brand-storybook	Patch

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[github-actions]

🟢 No design token changes found

[github-actions]

🟢 No unit test coverage changes found

All components and hooks with tests maintain the same coverage as the main branch.

[Copilot]

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 1
• Review effort level: Balanced

[github-actions]

🟢 Bundle size report

Check	Main	Branch	Change
UMD — full bundle (JS)	102.32 kB	102.32 kB	🟢 No change
UMD — full bundle (CSS)	67.94 kB	68.02 kB	⬆️ +84 B (+0.1%)
ESM — full bundle (JS + CSS)	1.59 MB	1.59 MB	⬆️ +431 B (+0.0%)
ESM — tree-shaken simple (Button)	71.22 kB	71.18 kB	✅ -47 B (-0.1%)
ESM — tree-shaken complex (ActionMenu)	80.13 kB	80.02 kB	✅ -116 B (-0.1%)

[github-actions]

⚠️ Visual differences found

Our visual comparison tests found UI differences.

Please review the differences by using the test artifacts to ensure that the changes were intentional.

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