新增: 父子任务支持(数据→后端→前端全链路,会话前基线收尾)

- df-nodes task_advance_node(父聚合推进)+ task.rs 命令(create parent_id 支持/delete 级联软删子任务)+ task_graph 工具

- 前端 Tasks 树形列表(折叠箭头/子进度徽章/缩进)+ 新建弹窗父任务下拉 + TaskDetail 父面包屑/子任务面板

- 设计文档: 父子任务支持设计-2026-08-04

src/stores/project/tasks.ts

@@ -22,7 +22,17 @@ export function createTasksStore() {
     })
   }
 
-  async function createTask(input: { project_id: ProjectId; title: string; description?: string; priority?: number; branch_name?: string; assignee?: string; idea_id?: string }) {
+  async function createTask(input: {
+    project_id: ProjectId
+    title: string
+    description?: string
+    priority?: number
+    branch_name?: string
+    assignee?: string
+    idea_id?: string
+    /** 父任务 ID(1 级嵌套,可空);传空串后端视为 None */
+    parent_id?: string | null
+  }) {
     const record = await runWithCatch(state, t('tasks.err.createFailed'), async () => {
       const r = await taskApi.create(input)
       state.tasks.push(r)
@@ -43,8 +53,10 @@ export function createTasksStore() {
 
   async function deleteTask(id: string) {
     await runWithCatch(state, t('tasks.err.deleteFailed'), async () => {
+      // 后端已级联软删子任务(delete_task 返回 { ok, cascaded });
+      // 本地同步移除父任务 + 其直接子任务(1 级嵌套,防悬挂 parent_id)
       await taskApi.delete(id)
-      state.tasks = state.tasks.filter(t => t.id !== id)
+      state.tasks = state.tasks.filter(t => t.id !== id && t.parent_id !== id)
     })
   }