The tagged ISO workflow fetched bos-settings/src/Cargo.toml from the
dev branch (404 after the Tauri split) and cargo-built bread-theme.
bread-theme 0.7.1 is already on the stable index. Stage required bins,
units, breadhelp content, and desktop/license files from the
minisign-verified index instead; optional bread-emit/module-host skip
until bread publishes them. Fail the bake if a required bin is missing.
Derive BREAD_BINS from iso/bread-lockfile.toml and fail the bake when a
listed binary or breadhelp content is missing. Bake bakery share files
and drop breadcast from the copied installed.json. Add WebKitGTK 4.1 for
Tauri bos-settings, remove rustup, and rewrite README/DESIGN to match the
ISO+skel tree.
