v0.13.1

Fixed

• Durable model, tool and delegated-agent activations begun inside an agent iteration now carry that iteration as a reader-only display parent, so Studio nests them under the iteration instead of beside the owning workflow step (AGNT5-1101). Durable ownership, activation identity, digests and replay are unchanged. BeginActivationRequest gains display_parent_correlation_id, forwarded by the native extension; runtimes that predate the field ignore it.