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/mock/handler.ts

@@ -1452,20 +1452,32 @@ function route(m: string, path: string, seg: string[], q: URLSearchParams, b: Re
     if (b.action === "cancel") {
       const index = mockIntents.findIndex((item) => item.id === id);
       const intent = mockIntents[index];
-      if (!intent || intent.inherited || (intent.state !== "running" && intent.state !== "paused")) {
+      if (
+        !intent ||
+        intent.inherited ||
+        (intent.state !== "running" && intent.state !== "paused" && intent.state !== "open")
+      ) {
         throw new Error("Worker 状态已变化");
       }
-      mockIntents.splice(index, 1);
-      return {
-        id: Number(id.replace(/\D/g, "")) || 0,
-        state: "cancelled",
-        deleted: {
-          intents: 1,
-          facts: 1,
-          findings: 1,
-          activities: mockActivity.filter((item) => item.intent_id === id).length,
-        },
-      };
+      const numId = Number(id.replace(/\D/g, "")) || 0;
+      if (b.mode === "hard") {
+        // 真删除:从列表移除,返回级联删除计数。
+        mockIntents.splice(index, 1);
+        return {
+          id: numId,
+          state: "",
+          deleted: {
+            intents: 1,
+            facts: 1,
+            findings: 1,
+            activities: mockActivity.filter((item) => item.intent_id === id).length,
+          },
+        };
+      }
+      // 假删除(默认):置 deleted + 记删除原因,保留节点。
+      intent.state = "deleted";
+      intent.delete_reason = String(b.reason ?? "");
+      return { id: numId, state: "deleted" };
     }
     const action = b.action === "resume" ? "resume" : "pause";
     const result = controlMockIntent(id, action);