Available runners: rust, golang, node
Test job: runs-on rust with container rust:1-bookworm (modern glibc)
Build job: runs-on golang with container docker:27-cli (same as before)
Old 'rust' runner had stale glibc causing linker failures.
Now uses 'docker' runner (same as other repos) with explicit
rust:1-bookworm container image (modern glibc).
Added cargo cache step for faster builds.