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/components/messages/CollapsedReadSearchContent.tsx

@@ -57,7 +57,7 @@ function VerboseToolUse({
   theme: ThemeName;
 }): React.ReactNode {
   const bg = useSelectedMessageBg();
-  // Same REPL-primitive fallback as getToolSearchOrReadInfo — REPL mode strips
+  // Same REPL-primitive fallback as getSearchExtraToolsOrReadInfo — REPL mode strips
   // these from the execution tools list, but virtual messages still need them
   // to render in verbose mode.
   const tool = findToolByName(tools, content.name) ?? findToolByName(getReplPrimitiveTools(), content.name);