feat(conductor): Plan-and-Execute 패턴 - Central Planner + Tier executor (env AGENT_MODE)

feat(observability): LangSmith 통합 (wrap_openai + @traceable on 4-Tier agents)

feat(orchestrator): 조건부 라우팅 추가 (severity gate + cause confidence retry)

feat(cause): Tier 2를 agentic RAG로 전환 (tool calling loop + synthesis)

feat: PHM 2016 CMP 통합 + 3개 알람 실데이터 동작

feat: Tier 2 원인 분석 LLM+RAG 구현

chore: FabAgent 골격 구성