test: retain created knowledge bindings across polling

Model persisted library state in the external-binding fixture instead of returning pre-creation data to background refreshes. Keep all selected and excluded library assertions, without assuming the last snapshot request belongs to the new library. Windows App: 300 passed; complete frozen Linux suite: 5371 passed, 51 skipped. Typecheck, lint and bilingual notes validation passed.

docs/development/release-preparation-0.15.0.md

@@ -185,6 +185,16 @@ Agent 产品源码及 Runtime 锁未因这四项改变，Agent
 Windows 原生 Runtime 聚焦用例、类型检查和 lint 通过。
 提交仅追加本段记录；仍须等待修正候选的主分支 CI 和生产构建。
 
+`706726b` 的桌面 [CI 36345672365](https://github.com/mesalogo/goodbuddy/actions/runs/36345672365)
+已通过上述采集与 Runtime 用例，但另一个外部知识库测试失败：
+5,370 通过、51 跳过、1 失败，生产构建未执行。
+该 fixture 只在查询新库 ID 时返回包含已创建库的快照，普通轮询会返回创建前数据；
+同时错误地要求最后一次请求必须属于新库，忽略后台轮询。
+改为模拟已持久化的库列表，等待新库请求发生，保留原库与新增库选中、被排除库未选中的
+全部界面断言，不修改产品代码。Windows 完整 App 300 项通过，类型、lint 和说明校验通过。
+冻结 tree `42a92450ad7d9ebc50167c7946bff53cff2889e6` 的 Linux 全量为
+**5,371 通过、51 跳过、0 失败**，耗时 748.67 秒。
+
 ## 数据、兼容与验收边界
 
 Desktop schema 48 新增魔法笔记会话来源元数据。升级前应备份完整用户数据，

src/renderer/src/App.test.tsx

@@ -7391,13 +7391,18 @@ describe("App", () => {
     const created = { ...existing, id: '33333333-3333-4333-8333-333333333333', name: 'Remote handbook', external: { knowledgeBaseId: '33333333-3333-4333-8333-333333333333', instanceId: instance.id, provider: 'dify' as const, remoteKnowledgeBaseId: 'remote-1', remoteName: 'Remote handbook', commonConfig: { resultLimit: 6, requestTimeoutMs: 15000, maxSnippetCharacters: 4000 }, providerConfig: { provider: 'dify' as const, useDatasetDefaults: true as const }, lastVerifiedAt: '2026-09-12' } };
     const initial = { libraries: [existing, excluded], selectedLibraryId: existing.id, sources: [], documents: [], graphNodes: [], graphRelations: [], evidence: [] };
     const updated = { ...initial, libraries: [...initial.libraries, created], selectedLibraryId: created.id };
-    vi.mocked(api.knowledge.getSnapshot).mockImplementation(async (libraryId) =>
+    let persistedSnapshot = initial;
-      libraryId === created.id ? updated : initial
+    vi.mocked(api.knowledge.getSnapshot).mockImplementation(async (libraryId) => ({
-    );
+      ...persistedSnapshot,
+      selectedLibraryId: libraryId ?? persistedSnapshot.selectedLibraryId,
+    }));
     vi.mocked(api.knowledge.externalInstancesList).mockResolvedValue([instance]);
     vi.mocked(api.knowledge.externalCatalogList).mockResolvedValueOnce({ items: [{ id: 'remote-1', name: 'Remote handbook' }], hasMore: false });
     vi.mocked(api.knowledge.externalCatalogGet).mockResolvedValueOnce({ id: 'remote-1', name: 'Remote handbook' });
-    vi.mocked(api.knowledge.externalBindingsCreate).mockResolvedValueOnce(updated);
+    vi.mocked(api.knowledge.externalBindingsCreate).mockImplementationOnce(async () => {
+      persistedSnapshot = updated;
+      return updated;
+    });
     vi.mocked(api.conversations.list).mockResolvedValueOnce([{ id: '44444444-4444-4444-8444-444444444444', projectId, title: 'External scope test', updatedAt: 200, messages: [], knowledgeLibraryIds: [existing.id] }]);
     render(<App />);
     await screen.findByRole('button', { name: /^External scope test/u });
@@ -7412,7 +7417,8 @@ describe("App", () => {
     await waitFor(() => expect(screen.getByRole('button', { name: '添加知识库' })).toBeEnabled());
     fireEvent.click(screen.getByRole('button', { name: '添加知识库' }));
     await screen.findByRole('heading', { name: 'Remote handbook' }, { timeout: 5_000 });
-    await waitFor(() => expect(api.knowledge.getSnapshot).toHaveBeenLastCalledWith(created.id));
+    // Polling can also refresh another selection; every snapshot must retain the created binding.
+    await waitFor(() => expect(api.knowledge.getSnapshot).toHaveBeenCalledWith(created.id));
     fireEvent.click(screen.getByRole('button', { name: /^External scope test/u }));
     openComposerOptions();
     fireEvent.click(await screen.findByRole('button', { name: '选择知识库，本次已启用 2 个' }));