feat(tasks): 总览页支持任务测试范围的查看/增删

- db: 新增 DeleteTaskScope；AddAgentScope 加 source 参数区分 agent/manual
- server: 新增 POST/DELETE /api/tasks/{id}/scope 端点
- web: 总览页新增「测试范围」卡片，可按类型手动增删，继承范围只读

Claude-Session: https://claude.ai/code/session_014TfZWeVGhjXqZD3vcj44mz

web/src/lib/mock/handler.ts

@@ -149,6 +149,12 @@ function route(m: string, path: string, seg: string[], q: URLSearchParams, b: Re
   if (seg[0] === "tasks" && seg[2] === "coverage-graph") return D.coverageGraph;
   if (seg[0] === "tasks" && seg[2] === "asset-refs") return D.assetRefsFor(Number(q.get("asset_id") ?? 0));
 
+  // ── 任务测试范围（增删查）──
+  if (seg[0] === "tasks" && seg[2] === "scope" && seg.length === 3 && m === "GET") return { scope: [] };
+  if (seg[0] === "tasks" && seg[2] === "scope" && seg.length === 3 && m === "POST")
+    return { id: Date.now(), task_id: Number(seg[1]), kind: b.kind, domain: b.value, source: "manual" };
+  if (seg[0] === "tasks" && seg[2] === "scope" && seg.length === 4 && m === "DELETE") return { ok: true };
+
   // ── 工作空间文件管理器（demo：静态示例树；写/建/删走下方写兜底 {ok:true}）──
   if (path === "/workspace/list") return D.workspaceList(q.get("path") ?? "");
   if (path === "/workspace/read") return D.workspaceRead(q.get("path") ?? "");