NS1 is marchon@70.88.205.138 using ~/.ssh/id_ed25519. Private key
bytes stay off git. Spawn, health, and kill go through ssh; remote
workers bind loopback only.
machines.json plus Add-machine UI place copies on the least-loaded host.
Monitor samples processing RTT and displays min, avg, p50, and p90 for
capacity planning. Remote hosts run src/agent.js.
