Each distro now builds amd64 on ubuntu-latest and arm64 on
ubuntu-24.04-arm instead of emulating arm64 under QEMU. image.sh gains
--platform, which pushes one <version>-<arch> tag, and --merge, which
joins those tags under the release, stable and alias tags with
buildx imagetools. The workflow splits into prepare, build and merge
jobs; scripts/build/publish.sh follows the same sequence locally.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
