Expand description
Runs and steps (RFC 0027 §6–§7, RFC 0026 §3): arming start nodes,
turning start events into durable runs, scheduling ready steps every tick,
executing the P3 step kinds (data steps in-loop, MCP calls on executor
threads, agent/think in turn workers, sleep on durable timers,
finish closing the run), retries + on_error routing, and the
workflow.* tools.