Routes the release build/test steps and a new fast pre-release
check.yml through ci/build.sh, which delegates to bread-ecosystem's
pinned shared Containerfile/build.sh instead of building against
whatever the bare hestia runner happens to have installed. Follows
the pattern already proven in breadpad. No extra ci/deps.txt: bread's
system_deps (systemd-libs, openssl, zlib) are all already pulled in
transitively by the shared image's base + git packages.
