Agent Effect System overview

Agent Effect System as a cross-cutting topic - the effect execution model that drives agent orchestration. The lifecycle is: task requested (process calls ctx.task/ctx.breakpoint/ctx.sleepUntil), effect pending (runtime throws an effect-pending exception), effect executed (external orchestration resolves the effect via babysitter task:post), result posted (next replay iteration advances deterministically). Effect kinds include agent (sub-agent dispatch), shell (command execution), skill (skill invocation), breakpoint (human approval gate), and sleep (time gate). The effect system enables deterministic replay and recovery.