testnet: amaru relays self-bootstrap
Drop the standalone bootstrap-producer service. Each amaru-relay-N now mounts its paired producer's pN-state and pN-configs read-only and runs the bootstrap retry loop in its own entrypoint, then exec /bin/amaru run. Antithesis 'setup complete' fires as soon as every container is service_started (seconds), instead of waiting for the unbounded bootstrap to finish inside the 6-minute setup window. Bootstrap proceeds during the test phase. The inline script preserves the existing exit-code contract (0, transient 1/2/5/7, hard otherwise) and adds a .bootstrap-complete sentinel so container restarts mid-promotion don't surface a half-written bundle to amaru run. Volumes amaru-bundle and bootstrap-state are gone; per-relay scratch lives on the existing aN-state volumes. scripts/smoke-test.sh: drop the bootstrap-producer wait gate; the existing per-relay bundle gate is now the equivalent readiness check. Spec/plan: specs/080-amaru-self-bootstrap/