Clean up legacy blog post link rot (~30 dead links across 2015-2018 posts)

[jmxpearson]

Summary

The lychee link checker added in PR #32 surfaced ~30 dead links across older _posts/ (2015-2018). The site-health.yml workflow currently excludes the entire blog directory (--exclude-path _site/blog) so these don't gate PRs.

Sample of what's broken

• http://people.duke.edu/~sni/* (5+ deleted personal-page assets)
• http://nasher.duke.edu/faculty/... (site reorganized)
• https://dibs.duke.edu/scholars/elizabeth-johnson and dibs.duke.edu/events/... (pages moved/deleted)
• https://bassconnections.duke.edu/project-teams/... (old project page)
• https://medschool.duke.edu/research/.../basic-science-day (moved)
• https://www.neuro.duke.edu/people/faculty/eva-naumann (moved)
• https://livestream.com/naturalsciences/Cafe (livestream URLs gone)
• http://www.upenn.edu/pennnews/news/michael-platt-... (Penn news article moved)
• http://research.vtc.vt.edu/people/read-montague/team (moved)
• http://www.sdsc.edu/~bourne/ (gone)
• http://emuseum.nasher.duke.edu/... (returns 400 Bad Request; API changed)
• 3-4 [ERROR] connection failures (changlab.net, kellyraechi.com, etc. — possibly defunct)

Full list available by running lychee --config ./lychee.toml --no-progress --root-dir "$(pwd)/_site" _site locally without the blog exclude (or just see the lychee report from PR #32 commit 59c3abb).

Acceptance

For each error, decide one of:

• Update: replace with the page's current URL
• Archive: swap to an Internet Archive snapshot (https://web.archive.org/web/<timestamp>/<url>)
• Remove link: keep the surrounding prose, drop the <a> / [text](url) markup
• Remove sentence: rare; only if the linked content was the entire point

Then drop --exclude-path _site/blog from .github/workflows/site-health.yml so blog posts get ongoing checking.

Notes

• This is editorial work, not infrastructure. Could be split into one issue per post if helpful.
• Consider doing this after the dibs-web01 migration so we know the link checker is reliably catching the relevant cases.