feat(mock): 补全新功能的 mock 数据(覆盖度/覆盖图/关联/工作空间)

- data：coverage、coverageGraph(11 节点树)、assetRefsFor、WS_TREE +
  workspaceList/Read 示例文件树
- handler：/tasks/{id}/coverage · coverage-graph · asset-refs +
  /workspace/list · read 路由(写/建/删走 {ok:true} 兜底)
- api：workspaceUpload/Download 加 MOCK 守卫(裸 fetch 绕过 http 助手，
  demo 下改为 no-op/占位下载，不再网络报错)

Co-Authored-By: Claude Opus 4.8 <[email protected]>

web/src/lib/mock/handler.ts

@@ -42,6 +42,15 @@ function route(m: string, path: string, seg: string[], q: URLSearchParams, b: Re
   if (seg[0] === "tasks" && seg[2] === "chat" && seg[3] === "stop") return { status: "stopped" };
   if (path === "/active") return { active: String(b.id ?? D.ACTIVE_TASK) };
 
+  // ── 覆盖度 / 覆盖图 / 资产关联（任务维度）──
+  if (seg[0] === "tasks" && seg[2] === "coverage" && seg.length === 3) return D.coverage;
+  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));
+
+  // ── 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") ?? "");
+
   // ── stats ──
   if (path === "/stats") return D.stats(task);