test(deploy): validate _universal path with a live 2-VM deploy on real Proxmox

[pparage]

Every backend and playbook test stubs runner.start() or only runs --syntax-check. The _universal path has never executed against a real Proxmox: idempotency tags, per-team VMID math, ansible-runner subprocess, and proxmox-controller action contracts are unverified. Add a real end-to-end deploy of a small (2-VM) topology and capture the result.