Project durable workflow handoffs as work items

docs/ENGINE_EDITOR_SPLIT.md

@@ -135,3 +135,21 @@ baseline revision inactive when an older revision is active, and fails closed
 when required capabilities or interfaces are absent. Baselines are immutable;
 editing derives a pinned local override, and reset archives that override
 without removing revision or instance history.
+
+## Common Work Inbox
+
+Workflow Engine also projects the current human handoff of a waiting instance
+through Core's versioned work-item provider contract. Tasks may aggregate that
+projection when it is enabled, while Workflow Engine remains the sole owner of
+the instance, step, allowed actions, and completion state.
+
+Human activities and reviews accept account, group, role, function, and
+function-assignment responsibility references. A missing assignee defaults to
+the account that started the instance. `due_after` uses the same bounded
+duration syntax as Workflow timers (`5m`, `2h`, `1d`, or ISO 8601). The Engine
+materializes assignment and due-date columns on the current step so inbox reads
+remain tenant-scoped and indexed; historical JSON handoffs are interpreted
+conservatively for upgrade compatibility. Automated waits and in-flight
+provider calls are not presented as human work. Recovery-required, unknown,
+dependency, and failed handoffs appear as blocked work and always link back to
+the pinned Workflow instance.