The payload (pure-stdlib bridge.py + a stock CPython closure) is fully
Nix-expressible, so this is NOT an escape-hatch/buildkit repo: both arches
build on emmett (amd64 native + arm64 pkgsCross of stock python3 from the
binary cache) with no buildkit, qemu, docker daemon, or howard pin.
Replace the partial amd64-only scaffold with parity-lib's
mkNix2ContainerPublish, completing the arm64 leg + multi-arch index. The
per-arch nix2container image derivations are kept verbatim; stage/publish/
publish-index/publish/push-staged now come from the shared builder so CI and
local invoke identical code. Thin .woodpecker.yaml to a single
nix run .#publish; retire the buildx/remote-builder steps.
The Dockerfile is now unused (the cutover drops it) but kept in-tree so the
server-side hadolint pre-receive hook does not crash on a file deletion.
Refs cluster #192, emmett#44.