op-devstack: sysgo component and admin/test RPC for lokahi

A sysgo component launching the out-of-process lokahi binary (kona-node's log-line RPC handshake pattern) plus the first slice of lokahi's admin/test RPC; the RPC surface grows with later phases (pause/resume interop and backfill/verification introspection for phase 3, restart-with-fresh-datadir for phase 4). Gate: 2-chain smoke test — both chains sync, per-chain RPC answers, one EL down stalls only its chain.

Depends on: #22532.

🤖 *Co-created with Claude (Fable 5)*

Start with dependency issue #22532 and the kona-node log-line RPC handshake pattern mentioned in the issue. Trace the op-devstack sysgo entry point, the lokahi binary launch, and the admin/test RPC surface. Done means the 2-chain smoke test passes: both chains sync, each per-chain RPC answers, and taking down one execution layer stalls only its chain.

Written by the indexing model from the issue text.