Agent state machine, policy, scheduling, and lifecycle events

rho_prompt() and rho_continue() return tasks. The agent consumes typed assistant events, schedules tool tasks, preserves source-order results, and emits typed lifecycle events. Steering and follow-up queues have separate, typed draining policies.

Details

Policy and scheduling decisions are S7 generics. Packages can specialize context transformation, before/after-tool behavior, next-turn preparation, assistant event reduction, queue draining, and tool batch execution without replacing the core loop.