Fleet now spawns the real zappier and middleware processes. Metered
timestamp/receipt/hash calls proxy to middleware when ZAPPIER_UPSTREAM
is set. CS credits, sales per-customer pricing, and QuickBooks export
are separate repos plugged into zappier-edge admin.
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.
