事件映射

Pi/Harness 事实	HarnessEvent	assistant-ui/Timeline
prompt accepted	`run.started`	running
message text delta	`assistant.delta`	合并文本
assistant message end	`assistant.completed`	complete
tool execution start/end	`tool.requested/completed/failed`	Tool 卡片/Timeline
broker pending/resolved	`approval.required/resolved`	Dialog 与卡片状态
canonical Skill read start/success	`skill.requested/loaded`	Catalog 高亮

未知 Pi 事件安全忽略。EventStore 原子分配 Session 内 sequence，客户端以 eventId 去重。