feat(intent): 意图删除支持假删除/真删除两种模式

删除入口区分两种模式(待领/运行中/已暂停的意图均可删除):

- 假删除(默认):意图置 state='deleted'、删除原因记入新字段 delete_reason,
  保留节点与全部产出/血缘,不再在图上另挂 fact。
- 真删除:物理删除意图及「仅由它支撑」的独占子孙(沿 yields/derived_from
  级联到叶子),避免孤立数据;共享节点、目标、任务根事实保留。被删意图先做
  token rollup 并清理 activity/副会话,被删 finding 先删 findings 行。

两种模式都照常用 cancelled 触发通知 planner(带删除前捕获的意图摘要 + 原因),
planner 文案不再声称原因挂为事实。

- DB: 新增 SoftDeleteIntent、重写 CancelIntent 为深度独占级联;schema 加
  delete_reason 列与 intent 的 deleted 状态(含旧库迁移)。
- 前端: 删除对话框加模式切换与动态说明,状态徽章/图标新增「已删除」,
  播报板展开展示删除原因。

web/src/lib/api.ts

@@ -315,12 +315,19 @@ export const api = {
   deleteTaskArchive: (id: number) => del<TaskArchive>(`/task-archives/${id}`),
   deleteTaskArchives: (archiveIds: number[]) =>
     post<{ items: ArchiveBatchItem[] }>("/task-archives/delete/batch", { archive_ids: archiveIds }),
-  controlIntent: (taskId: string, intentId: string, action: "pause" | "resume" | "cancel", reason?: string) =>
+  controlIntent: (
+    taskId: string,
+    intentId: string,
+    action: "pause" | "resume" | "cancel",
+    reason?: string,
+    // cancel 专用:soft(默认,假删除,意图置 deleted + 记删除原因)| hard(真删除,级联移除独占子孙)。
+    mode?: "soft" | "hard",
+  ) =>
     post<{
       id: number;
-      state: "paused" | "open" | "stopped";
+      state: "paused" | "open" | "deleted" | "";
       deleted?: { intents: number; facts: number; findings: number; activities: number };
-    }>(`/tasks/${taskId}/intents/${intentId}/control`, { action, reason: reason ?? "" }),
+    }>(`/tasks/${taskId}/intents/${intentId}/control`, { action, reason: reason ?? "", mode: mode ?? "soft" }),
   sendWorkerMessage: (taskId: string, intentId: string, message: string, requestId: string) =>
     post<{
       id: number;