The game repo grew from a single genre/song count to 18 genres (119
synth-orchestra songs + 120 drum patterns), gamepad remap, and multiplayer,
and added its own Dockerfile/nginx.conf/.dockerignore specifically so only
index.html gets served. This service had fallen behind on both fronts: it
bind-mounted the whole cloned repo into nginx:alpine, publicly serving
README.md, CLAUDE.md, DEPLOYMENT.md, the Dockerfile itself, and old
versions_to_compare/*.html snapshots alongside the game. Build from the
repo's own Dockerfile instead (matching its .dockerignore) so only the game
is served, with gzip and /healthz along for free, and refresh the written
README's stale feature description.