Hotfix to SubNav

[rezrah]

Summary

Towards https://github.com/github/brand-marketing-design/issues/2606

Patches the unreleased features for SubNav, specifically:

List of notable changes:

• adjustments to padding
• removal of Mozilla browser overrides, which aren't needed in Dotcom

Steps to test:

1. See this story

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

• See Slack

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]

⚠️ No Changeset found

Latest commit: 285f22a

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[Copilot]

Pull request overview

This PR implements a hotfix for the unreleased SubNav component, addressing padding inconsistencies and removing unnecessary Mozilla Firefox-specific CSS overrides. The changes improve visual alignment and simplify the CSS by eliminating browser-specific workarounds that are no longer needed.

Changes:

• Adjusted padding on active link pills in mobile overlay to use asymmetric values for better optical alignment
• Removed optical alignment hack (top: 1px) that was previously applied to all overlay links
• Removed Firefox-specific CSS overrides that are no longer necessary

Reviewed changes

Copilot reviewed 1 out of 15 changed files in this pull request and generated no comments.

File	Description
packages/react/src/SubNav/SubNav.module.css	Updated padding from 2-value to 3-value shorthand for active links in overlay (line 373), removed optical alignment adjustment (lines 595-596), and removed Firefox-specific @supports block (lines 713-717)
Visual snapshot files (8 PNG files)	Auto-generated visual regression test snapshots updated to reflect the CSS padding and alignment changes

[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.

[github-actions]

🟢 No visual differences found

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