feat(intents): 删除 work 改为「停止+记录原因」,不再销毁数据

删除不再删意图与其产出,而是:停到 stopped、要求填写删除原因、把原因作为
事实挂到该意图上、并写进意图 payload,规划者收到 cancelled 触发(意图内容+原因)。

- db: StopIntentWithReason —— 标 stopped + 建原因事实 + 连边 + 合并 payload
  (cancelled_by_user/cancel_reason),单事务;旧 CancelIntent 保留不再被调用
- agent/server: renderTriggers 加 cancelled 分支;Task.NotifyCancelled;
  controlIntent/applyIntentControl 接收并要求 reason
- web: 删除弹窗改为必填原因的 Textarea;列表用红色垃圾桶+删除线+「已删除」徽标
  区分;选中会话顶部横幅展示删除原因;controlIntent 传 reason

Claude-Session: https://claude.ai/code/session_019QXSCDmzimwnjntBNCgUD7

web/src/lib/api.ts

@@ -227,12 +227,12 @@ export const api = {
     post<{ id: string; paused: boolean; queued: boolean; status: string }>(`/tasks/${id}/control`, { action }),
   controlTasksBatch: (taskIds: string[], action: "pause" | "resume") =>
     post<{ items: BatchControlItem[] }>("/tasks/control/batch", { task_ids: taskIds, action }),
-  controlIntent: (taskId: string, intentId: string, action: "pause" | "resume" | "cancel") =>
+  controlIntent: (taskId: string, intentId: string, action: "pause" | "resume" | "cancel", reason?: string) =>
     post<{
       id: number;
-      state: "paused" | "open" | "cancelled";
+      state: "paused" | "open" | "stopped";
       deleted?: { intents: number; facts: number; findings: number; activities: number };
-    }>(`/tasks/${taskId}/intents/${intentId}/control`, { action }),
+    }>(`/tasks/${taskId}/intents/${intentId}/control`, { action, reason: reason ?? "" }),
   taskLLMResolution: (id: string) => get<TaskLLMResolutions>(`/tasks/${id}/llm/resolution`),
   // 重跑一条没跑成功的意图(blocked/exhausted/stopped)：置回 open，worker 会重新认领、从头再跑。
   rerunIntent: (taskId: string, intentId: string) =>