- postpone pruning / interface auto-detection to top task-level
only the task state knows for sure, that it requires its wrapped child to push to both ends
- perform connectivity validation only after pruning
only then, we the interfaces are completely determined
works if propagation direction can be derived from a generator or
connecting stage within the sequence
start-to-end propagation through whole serial container still fails
- store "failure" solutions to facilitate debugging
- Introspection assigns solution IDs as soon as they are created in a stage
Thus, solution IDs represent their creation order.
In contrast, the order of publishing (in StageStatistics) should
represent the cost order.
- Storing failures is disabled if Introspection is not available.