RunContext

What a running task knows: the run's RunConfig, its own RunPosition, and its event channels.

emit records a durable custom event: it is committed with this task's result, given a per-thread sequence number in that commit, delivered only after the commit and replayed to later subscribers. It is discarded if the task fails. progress is live-only, for token deltas and similar high-volume progress: delivered at once to current subscribers, never persisted or replayed. Outside a GraphRuntime both are no-ops.