docs: 添加 ToolSearch 设计指南 + 禁用 turn-zero 工具推荐弹窗

- 新增 docs/design/tool-search-design-guide.md，涵盖架构、搜索算法、执行管道、演进历史
- 禁用 getTurnZeroSearchExtraToolsPrefetch，消除用户输入时的频繁弹窗
- inter-turn 发现机制保持不变

Co-Authored-By: glm-5-turbo <zai-org@claude-code-best.win>

src/tasks/LocalAgentTask/__tests__/LocalAgentTask.test.ts

@@ -88,7 +88,7 @@ mock.module('src/services/analytics/index.js', () => ({
 }))
 
 mock.module('src/utils/collapseReadSearch.js', () => ({
-  getToolSearchOrReadInfo: () => undefined,
+  getSearchExtraToolsOrReadInfo: () => undefined,
 }))
 
 // ─── Import after mocks ───