refactor(camera): 移除相机跟随的线性插值逻辑

直接使用目标位置作为焦点，简化相机跟随实现

Game/include/camera/GameCameraController.h

@@ -46,7 +46,6 @@ private:
   bool initialized_ = false;
 
   float zoom_ = 1.2f;
-  float followLerpSpeed_ = 8.0f;
   float debugMoveSpeed_ = 800.0f;
 };
 

Game/src/camera/GameCameraController.cpp

@@ -89,9 +89,7 @@ void GameCameraController::Update(float deltaTime) {
   }
 
   if (target_) {
-    Vec2 targetFocus = target_->GetPosition();
+    focus_ = target_->GetPosition();
-    float t = std::clamp(deltaTime * followLerpSpeed_, 0.0f, 1.0f);
-    focus_ = focus_ + (targetFocus - focus_) * t;
   } else if (debugEnabled_) {
     updateDebugInput(deltaTime);
   }