fix(arch-030,arch-047): workflow steps resolve plugins via contracts at runtime

app/plugins/builtins/dms/contracts.py

@@ -15,6 +15,11 @@ class DmsContract:
     DmsFile = DmsFile
     Folder = Folder
 
+    @classmethod
+    def get_function(cls, name: str):
+        """Return a callable exposed by this contract, or None if absent."""
+        return getattr(cls, name, None)
+
 
 # ─── self-registration ───