feat: semantically determine goal completion

ref: N25B-432

src/control_backend/schemas/belief_list.py

@@ -1,6 +1,7 @@
 from pydantic import BaseModel
 
 from control_backend.schemas.program import Belief as ProgramBelief
+from control_backend.schemas.program import Goal
 
 
 class BeliefList(BaseModel):
@@ -12,3 +13,7 @@ class BeliefList(BaseModel):
     """
 
     beliefs: list[ProgramBelief]
+
+
+class GoalList(BaseModel):
+    goals: list[Goal]

src/control_backend/schemas/belief_message.py

@@ -13,6 +13,9 @@ class Belief(BaseModel):
     name: str
     arguments: list[str] | None
 
+    # To make it hashable
+    model_config = {"frozen": True}
+
 
 class BeliefMessage(BaseModel):
     """

src/control_backend/schemas/program.py

@@ -117,7 +117,7 @@ class Goal(ProgramElement):
     :ivar can_fail: Whether we can fail to achieve the goal after executing the plan.
     """
 
-    description: str
+    description: str = ""
     plan: Plan
     can_fail: bool = True