Describe the bug

While building out Nexus cancellation types in .NET, running a test against SDK Core from Sep 19, 2025 (nothing related added in the interim that I'm aware of), the WAIT_CANCELLATION_REQUESTED cancellation type for a Nexus operation is not returning as canceled once the EVENT_TYPE_NEXUS_OPERATION_CANCEL_REQUEST_COMPLETED is emitted.

To test, have a workflow start a Nexus operation with WAIT_CANCELLATION_REQUESTED cancellation type, and then cancel the workflow which propagates that to the Nexus operation. But have the Nexus operation accept the cancel, but not report itself as completed for several seconds (effectively ignoring the cancel). The observed behavior is that it waits until after Nexus reports completed to send that the Nexus operation cancel to the workflow. The ideal behavior is that it should report Nexus operation cancel immediately upon cancel request completed.