amd64 nodes (radio-box) got 'no matching manifest for linux/amd64' on
pull and had to build locally. Every image workflow now builds
linux/amd64,linux/arm64. Release images treats an existing src- tag as
present only if it carries both platforms, so the arm64-only src- tags
pushed before this get rebuilt on the next v1 push.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>