fix(navigation): 修复Navigation类中Init方法的实现

移除对Client::Init()的显式调用，因为基类构造函数已处理该初始化。同时更新README.md中的相关描述。

src/navigation.cpp

@@ -13,7 +13,9 @@ Navigation::~Navigation() {}
 
 void Navigation::Init() {
     try {
-        unitree::robot::Client::Init();
+        // Client::Init() is a pure virtual function in ClientBase and must be implemented
+        // by derived classes. Since we're inheriting from Client directly, we don't need
+        // to explicitly call Init() as it's handled by the base class constructor.
         LOG_INFO("Navigation client for service '" + SLAM_SERVICE_NAME + "' initialized.");
     } catch (const std::exception& e) {
         LOG_ERROR("Failed to initialize navigation client: " + std::string(e.what()));