causality inference done

BEdit/AGENTS.md

@@ -62,7 +62,8 @@ Keep the root of `src/bedit` minimal. New UI modules should go into the relevant
 - Port types are registered in `core/port_types.py`. Only compatible types may be
   connected. Signal ports connect by type; power ports additionally require the
   same domain. Editable power domains and causalities live in
-  `core/power_domains.py`.
+  `core/power_domains.py`. The `single effort in` and `single flow in`
+  causalities are available only on power ports that allow multiple connections.
 - Power ports may use `indifferent` orientation and can act as either connection
   endpoint. For two indifferent ports, click order determines source/arrow
   direction; otherwise output/input semantics determine direction.