Fix missing CSS namespace on active IDE tab class

[rezrah]

Summary

🧹 Tidying up

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:

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Before	After

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 27de2dda31b6ece7dc7b78289d877729c5441940

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

This PR includes changesets to release 7 packages

Name	Type
@primer/react-brand	Patch
@primer/brand-docs	Patch
@primer/brand-primitives	Patch
@primer/brand-e2e	Patch
@primer/brand-fonts	Patch
@primer/brand-config	Patch
@primer/brand-storybook	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[bot]]

🟢 No design token changes found

[github-actions[bot]]

⚠️ 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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If the changes are expected, please run npm run test:visual:update-snapshots to replace the previous fixtures.

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