Fix publication badge spacing and PlumX loading

[systemreliability]

Summary

• Increase and broaden the OpenAlex-to-Google Scholar badge spacing rule
• Load the PlumX popup widget globally so homepage selected publications render PlumX badges like the publications page
• Remove the duplicate PlumX script from the publications page
• Hide openalex_id from expanded BibTeX output through the custom BibTeX filter

Verification

• Ran git diff --check
• Ran bundle exec jekyll build
• Confirmed generated homepage includes PlumX badge markup and widget-popup.js
• Confirmed generated homepage/publications BibTeX output no longer contains openalex_id

Notes

Local Jekyll build completed successfully. The local machine still lacks ImageMagick convert, so the existing responsive image generation step logged convert: command not found warnings while Jekyll exited successfully.

[github-actions]

Failed prettier code check. Check this file for more information.