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

feat(orchestrator): Supervisor agent - LLM-driven dynamic workflow routing

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

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

feat: 에이전트 가시화 강화 (페르소나·SPC 차트·LangGraph)

feat: 4-Tier 오케스트레이터 구현

chore: FabAgent 골격 구성