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.
Central fleet.json sets min/max copies. Tree-node keepFloor respawns
until three healthy unpaused replicas remain. CLI and loopback UI
pause, resume, stop, and restart instances that fail health checks.
