- LeaseGuard gains an is_cancellation convenience property
- ActiveAssignmentRunner marks the lease lost with a cancellation
reason when a renewal response reports cancel_requested
- AssignmentExecutor threads stop_reason through to TaskRunner/
WorkflowRunner and maps a cancellation-flavored stop to
AssignmentExecutionResult.status = "cancelled" instead of "failed"
- AssignmentProcessor forwards a three-way done/cancelled/failed
status when reporting the terminal result
- Add/extend tests across lease, assignment, processor, and client
q792602257