Follow-up to #484. The first run of Runner base image (#13, run_01m5nt1x3ee8t9vv33cf88t0pr) on the workspace's runner, SYNTAQX-linux, got through checkout and the buildx step. build-base then failed with spawnSync cargo ENOENT.
Cause: the deploy tool reads the workspace's crates with cargo metadata (scripts/deploy/stack.mjs), and the runner's default job image, node:24-bookworm, has no Rust.
Change: a new step installs a minimal rustup toolchain when cargo is missing and adds it to GITHUB_PATH. The header comment now says so.
Checked: cargo test -p g1t-actions --test repository_workflows passes (24 tests). After this merges, I'll dispatch the workflow again.