fix: look for goals in steps rather than plans

small bugfix, we used to look for goals in plans, but they are part of
a plan.

ref: N25B-400

src/control_backend/agents/bdi/bdi_program_manager.py

@@ -198,9 +198,9 @@ class BDIProgramManager(BaseAgent):
         :return: All goals within and including the given goal.
         """
         goals: list[Goal] = [goal]
-        for plan in goal.plan:
-            if isinstance(plan, Goal):
-                goals.extend(BDIProgramManager._extract_goals_from_goal(plan))
+        for step in goal.plan.steps:
+            if isinstance(step, Goal):
+                goals.extend(BDIProgramManager._extract_goals_from_goal(step))
         return goals
 
     def _extract_current_goals(self) -> list[Goal]: