feat: add supervisor workspace and traceable story graph

Extend the existing heartbeat workspace with scoped work reviews, result-specific story graphs, source inspection, and pinned conversation or task feedback. Connect confirmed continuation and local knowledge entity previews through the desktop APIs, and preserve result history and user corrections in schema 43.

Include focused regression tests, an isolated visual fixture, and implementation evidence. Full event-by-event replay, Experiment targets, no-change handling, and cancellation remain incomplete; this commit does not claim complete feature acceptance. Existing automatic plans remain active when the application entry is disabled.

Release note: Review work progress in the Supervisor workspace, trace graph events to saved sources, and open a matching review from pinned conversation or task feedback.

docs/features/assistant-workbar/prd.md

@@ -107,6 +107,8 @@ Runtime
 使用门槛：
 
 - 监督默认选择当前会话，用户可以改选其他 Conversation、Task 或实验对象。
+
+当前监督卡片已支持 Conversation/Task 跟随与固定，绑定保存在 tasks 实例的 `targetRef`；绑定只影响监督卡片，任务列表继续跟随当前项目。实现范围与验证见[监督者进度](../conversation-supervision/progress.md)。实验对象仍属后续工作。
 - Runtime 默认跟随当前会话或 Task；执行事件可以查看，但 Job/Run 不作为独立选择对象。
 - 终端创建时固定到当前项目执行空间，由项目配置自动决定本机或托管 SSH；没有当前项目时
   使用本机 Home。