merge: maestro/tsk_PbcHccuPmwxV [任务取消/删除的 UI 入口]

# Conflicts:
#	web/style.css

src/store/store.ts

@@ -613,6 +613,43 @@ export class Store {
     return rows.map(rowToEvent).reverse();
   }
 
+  /**
+   * 彻底删除任务及其全部子孙（runs/approvals 由 FK CASCADE 自动清除，events 手动清理）。
+   * 不可恢复——调用方须在上层做二次确认。
+   */
+  deleteTask(taskId: string): { deleted: number } {
+    const root = this.getTaskRow(taskId);
+    if (!root) throw new StoreError(`任务不存在: ${taskId}`);
+
+    // BFS 收集所有子孙 id（用于清理 events，其他表有 FK ON DELETE CASCADE）
+    const toDelete: string[] = [];
+    const queue: string[] = [taskId];
+    while (queue.length) {
+      const tid = queue.shift()!;
+      toDelete.push(tid);
+      const kids = this.db.prepare(
+        `SELECT id FROM tasks WHERE parent_id = ?`,
+      ).all(tid) as Array<{ id: string }>;
+      for (const k of kids) queue.push(k.id);
+    }
+
+    const projectId = root.project_id;
+    const txn = this.db.transaction(() => {
+      // events 没有 FK，逐条清理
+      for (const tid of toDelete) {
+        this.db.prepare(`DELETE FROM events WHERE task_id = ?`).run(tid);
+      }
+      // 删根节点：子孙、runs、approvals 均 ON DELETE CASCADE
+      this.db.prepare(`DELETE FROM tasks WHERE id = ?`).run(taskId);
+    });
+    txn();
+
+    this.emit(projectId, null, 'task.updated', {
+      kind: 'delete', taskId, count: toDelete.length,
+    });
+    return { deleted: toDelete.length };
+  }
+
   /**
    * 取下一个可执行任务（叶子、ready、依赖全部 done）。供编排器领取。
    * 被拆解的 Hard 容器任务不会是 ready（停在 decomposed），天然排除。