Build unified Runtime upgrade and version discovery

Make Runtime able to describe itself and reliably replace or restart itself. Add public, read-only version metadata, miren version --server, and a per-process runtime_instance_id. Consolidate managed and standalone upgrades under miren upgrade.

Build the durable, idempotent lifecycle executor for restart and upgrade. It must survive termination of the Runtime process, verify readiness, and preserve rollback behavior. Keep miren server upgrade as a compatibility shim and report unsupported container installations clearly.