update version in chapter9

docs/chapter9/Chapter9-Context-Engineering.md

@@ -5,7 +5,7 @@ In previous chapters, we have introduced memory systems and RAG for agents. Howe
 To enable readers to quickly experience the complete functionality of this chapter, we provide a directly installable Python package. You can install the version corresponding to this chapter with the following command:
 
 ```bash
-pip install "hello-agents[all]==0.2.7"
+pip install "hello-agents[all]==0.2.8"
 ```
 
 This chapter mainly introduces the core concepts and practices of context engineering, and adds a context builder and two supporting tools to the HelloAgents framework:

docs/chapter9/第九章 上下文工程.md

@@ -5,7 +5,7 @@
 为了让读者能够快速体验本章的完整功能，我们提供了可直接安装的Python包。你可以通过以下命令安装本章对应的版本：
 
 ```bash
-pip install "hello-agents[all]==0.2.7"
+pip install "hello-agents[all]==0.2.8"
 ```
 
 本章主要介绍上下文工程的核心概念与实践，并在HelloAgents框架中新增了上下文构建器和两个配套工具：