Hello there, Im trying to reduce the db size by deleting some checkpoints and writes. However, Im not really sure what needs to stay there for HIL and to maintain state within a thread in an agent with several subagents. Should I leave the last checkpoint for a thread with empty ns? Should I worry about namespaces? Leaving the latest checkpoint seems to work but Im not really sure. I understand that I can configure stuff in langgraph.json but I would like to understand how checkpoints work. ...