feat: extract semantic beliefs from conversation

ref: N25B-380

src/control_backend/schemas/chat_history.py

@@ -0,0 +1,10 @@
+from pydantic import BaseModel
+
+
+class ChatMessage(BaseModel):
+    role: str
+    content: str
+
+
+class ChatHistory(BaseModel):
+    messages: list[ChatMessage]