Convert animated GIFs to MP4 to cut file size (~54 gifs, ~122 MB)

[jonfroehlich]

Convert animated GIFs to MP4 (file size)

The repo has ~54 .gif files totaling ~122 MB (16 referenced from published lessons). Animated GIFs are a very inefficient format; re-encoding to MP4 (H.264) typically cuts size by 5–10× with no additional quality loss for playback.

Important caveat: the GIFs' quality loss is already baked in (they were exported as GIF and the source files are long gone). Converting to MP4 won't restore quality, but it also won't lose more — and the files get much smaller / faster to load.

Scope

• Audit which GIFs are still referenced (start with the 16 in published .md).
• Re-encode referenced GIFs → MP4 (ffmpeg -i in.gif -c:v libx264 -crf 23 -pix_fmt yuv420p -movflags +faststart -an out.mp4).
• Swap the markdown: ![alt](x.gif) → an autoplay/loop/muted <video aria-label="…"> (matching the site's hero-video pattern; see website-dev.md), or keep <img> only where animation isn't needed.
• Remove orphaned/unreferenced GIFs.

Notes

• Coordinate with the movies/→videos/ dir consolidation (companion issue) since both touch the same asset folders — ideally do the rename first, then convert.
• The html-proofer link-check gate will catch any refs broken during the swap.
• signals/ GIFs: those notebooks are migrating to makeabilitylab/signals (Signals Lessons #116) — handle there, not here.

Part of V2.0.