New crate providing cargo and rustup step types for WFE workflows: Cargo steps: build, test, check, clippy, fmt, doc, publish Rustup steps: rust-install, rustup-toolchain, rustup-component, rustup-target Shared CargoConfig base with toolchain, package, features, release, target, profile, extra_args, env, working_dir, and timeout support. Toolchain override via rustup run for any cargo command.