本次主要解决「刷新或补流后前端与后端任务进度不同步」以及「同一条工具链路被画两遍」的问题：在加载会话后对仍在运行的任务自动挂载 task-events 补流；补流重绘过程详情后恢复 HITL 审批入口；为补流增加同会话单飞锁；并在主对话 POST 流读取期间用 __csAgentLiveStream 标记活跃流，避免与 task-events 双通道重复消费同一批事件（与人机协同是否开启无关）。
These changes fix post-refresh task progress falling behind and duplicate tool-call/tool-result rows in the timeline: after loading a conversation, the UI re-attaches the task-events replay when a task is still running; after replay redraws process details, HITL approval UI is restored; replay attachment is single-flight per conversation; and while the main chat POST stream is active, a __csAgentLiveStream guard blocks starting task-events so the same events are not handled twice (independent of HITL mode).