Document task cancellation latency in CLOUD_DEPLOYMENT.md (task-cancellation 8.1)

docs/CLOUD_DEPLOYMENT.md

@@ -540,6 +540,14 @@ device workflows to tolerate repeated actions when the target operation allows
 it. Do not use this release for operations that require a transactional
 exactly-once guarantee across the cloud database and an external device.
 
+Task cancellation is collaborative, not instantaneous, for tasks that have
+already left the queue. Cancelling a `queued` task takes effect immediately.
+Cancelling an `assigned`/`dispatched` task only records the request; the
+owning Host Agent learns about it at its next lease renewal (at most roughly
+one third of `lease_duration_seconds`, the same interval used for lease-loss
+detection) and then stops at the next cooperative checkpoint. As with lease
+loss, an action already sent to a device cannot be rolled back mid-flight.
+
 ## Shutdown And Rollback
 
 For a normal shutdown, stop Host Agents first so they stop polling, interrupt