Start with causality inference

BEdit/AGENTS.md

@@ -56,8 +56,9 @@ Keep the root of `src/bedit` minimal. New UI modules should go into the relevant
   anchors may change without changing IDs.
 - Parameters belong to `Component` rather than a particular implementation kind,
   so graph and text components share stable-ID name/type/value records.
-- Port orientation is presented as one unified list in the UI, while the model
-  indexes inputs and outputs separately for connection semantics.
+- Components store one ordered `ports` list. Each port's `orientation` field is
+  authoritative (`input`, `output`, or power-only `indifferent`); connection and
+  presentation code derives any directional groupings when needed.
 - 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
@@ -72,9 +73,15 @@ Keep the root of `src/bedit` minimal. New UI modules should go into the relevant
 - Port removal or reorientation must be rejected when it would invalidate an
   existing connection.
 - Connections reference port IDs, never port names.
+- Connections store their port type and bond-graph causality explicitly.
+  `core/bond_graph.py` owns causality inference; the simulation service invokes
+  it before Modelica composition. The controller copies inferred values into the
+  live model and refreshes the workspace before compile, export, or run.
+  Causality values are `none`, `source`, `target`, `warn_source`, and `warn_target`.
 - Connection junctions are explicit typed graph objects. Splitting a connection
   creates one incoming and one outgoing segment; the junction can source further
-  branches without overlapping full connection paths.
+  branches without overlapping full connection paths. Power bond connections
+  cannot contain junctions.
 - Graph interaction has separate Pointer and Connect modes. Port hints are only
   visible in Connect mode. Connecting two blocks opens the compatible port-pair
   chooser; explicit port clicks determine its default selection. Connections
@@ -324,6 +331,7 @@ PYTHONPATH=src python3 -m bedit
 ```
 
 The installed GUI entry point is `bedit.gui.app:main`.
+The first non-flag launch argument is opened as the initial document.
 
 ## Completion checklist