The aarch64 release leg runs on the klokka host. Gate the sccache / cargo-binstall / cargo-leptos installs to the ephemeral x86_64 container; on the bare runner check-and-fail instead (the sccache tarball was x86_64-only anyway, so it was both a host mutation and a wrong-arch binary). Switch checkout to v4 builtin:checkout (native Go, no Node/download) in all jobs. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>