Backfill compress existing 26 MB of images

[jmxpearson]

Summary

PR #32 added jpegoptim / oxipng / svgo pre-commit hooks (Phase 1) that compress images on commit. They only run on staged files, so the existing ~26 MB of legacy images in images/ stays untouched until each is modified.

A one-shot backfill would shrink the working tree by an estimated 30-60% (mostly from oversized JPGs like kevin.jpg at 3 MB and anne.jpg at 1.7 MB).

Approach

A maintainer runs pre-commit run --all-files (with the image hooks not skipped) and commits the result as a single dedicated PR. Note that .git history blob storage is not reduced — only the working tree and future clones benefit from the smaller files. Full .git reclaim would require git filter-repo and rewriting history, which we explicitly do not do here.

Acceptance

• One-shot run of all image hooks across images/ and images/icons/
• Verify visual quality of a representative sample (lab photos shouldn't look obviously degraded)
• Commit as a single chore: backfill image compression PR
• Drop du -sh images/ measurements before/after in the PR body

Notes

• Phase 2's size cap will block any image still over 1 MB after compression. Some legacy photos may need editorial downscaling first (e.g., kevin.jpg at 3 MB → ~600 KB after jpegoptim --max=85 is still too big; needs to be downscaled to a sane web resolution like 800px wide).
• .image-size-overrides is available for files that legitimately need to exceed 1 MB (high-res research figures).