feat: add system theme toggle

[araujogui]

Description

Add system theme toggle

Validation

Related Issues

Related to nodejs/doc-kit#597

Check List

• I have read the Contributing Guidelines and made commit messages that follow the guideline.
• I have run pnpm format to ensure the code follows the style guide.
• I have run pnpm test to check if all tests are passing.
• I have run pnpm build to check if the website builds without errors.
• I've covered new added functionality with unit tests if necessary.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
nodejs-org	Ready	Preview	Feb 25, 2026 8:29pm

[github-actions]

👋 Codeowner Review Request

The following codeowners have been identified for the changed files:

Team reviewers: @nodejs/nodejs-website

Please review the changes when you have a chance. Thank you! 🙏

[codecov]

Codecov Report

❌ Patch coverage is 67.64706% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.08%. Comparing base (3dd2deb) to head (ed1e50e).
⚠️ Report is 4 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...ges/ui-components/src/Common/ThemeToggle/index.tsx	67.64%	22 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8659      +/-   ##
==========================================
- Coverage   75.12%   75.08%   -0.05%     
==========================================
  Files         104      104              
  Lines        9098     9159      +61     
  Branches      314      315       +1     
==========================================
+ Hits         6835     6877      +42     
- Misses       2261     2280      +19     
  Partials        2        2              

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[mikeesto]

I think you might have linked to the wrong issue?

[AugustinMauroy]

Noice job

[github-actions]

Lighthouse Results

URL	Performance	Accessibility	Best Practices	SEO	Report
/en	🟢 98	🟢 93	🟢 100	🟢 100	🔗
/en/about	🟢 99	🟢 94	🟢 100	🟠 88	🔗
/en/about/previous-releases	🟢 98	🟢 97	🟢 100	🟢 100	🔗
/en/download	🟢 99	🟢 96	🟠 81	🟢 100	🔗
/en/download/archive/current	🟢 100	🟢 97	🟢 100	🟢 100	🔗
/en/blog	🟢 98	🟢 97	🟢 96	🟢 100	🔗

[canerakdas]

LGTM