- Added the `Worker` `max_eager_activity_reservations_per_workflow_task` option for configuring

the number of activity slots reserved for eager execution per workflow task. Configured values

must be positive; use `disable_eager_activity_execution` to disable eager activity execution.

overrides for this flag from `tests/worker/test_workflow.py`, and replace this rollout

note with a `Fixed` entry announcing the behavior change.

- Custom workflow runners that construct `WorkflowInstanceDetails` must now pass

- Marked system Nexus envelope payloads so nested payloads can be detected and

visited after the envelope is already stored as a payload.