Capstone: Production Multi-Agent Research Assistant

Build the final boss in 18-capstone-production-assistant. It combines advanced RAG, a LangGraph supervisor, human approval, Postgres checkpoints, LangSmith traces, evals, deployment, prompt-injection defense, and a cost cap. Small ask. Basically Tuesday.

• Runnable ingestion and retrieval pipeline with citations.
• Supervisor graph routing research, synthesis, and review workers.
• Human-in-the-loop approval for risky actions and expensive branches.
• Durable Postgres checkpointer with thread-level replay.
• LangSmith trace metadata, datasets, and regression evals.
• LangServe-compatible deployment surface with auth and rate limits.