The build no longer downloads Alpine.js. Its npm package tarball is
committed as 3p/alpinejs-3.14.9.tgz; its sha256 matches the value
script/fetch-assets pinned, and the cdn.min.js inside it matches the
value static/vendor.sha256 pinned.
make assets extracts package/dist/cdn.min.js to the ignored
static/js/alpine.min.js. make test, check, build and dev run it first,
and the Dockerfile builds through make test and make build.
script/fetch-assets, its Dockerfile step, static/vendor.sha256 and
static/vendor_test.go are removed, along with bootstrap's curl install.
Model: opus-5-5