refactor(character): 使用整数坐标优化角色位置同步

- 将CharacterWorldPosition改为使用整数坐标，避免浮点精度问题
- 添加位置余数处理，确保移动平滑性
- 统一角色位置同步逻辑到SyncActorPositionFromWorld方法
- 修改地图移动检测使用整数坐标判断

Game/src/world/GameTown.cpp

@@ -1,9 +1,20 @@
 #include "world/GameTown.h"
+#include "character/CharacterObject.h"
 #include <SDL2/SDL.h>
 #include <algorithm>
+#include <cmath>
 
 namespace frostbite2D {
 
+namespace {
+
+Vec2 RoundWorldPoint(const Vec2& pos) {
+  return Vec2(static_cast<float>(std::lround(pos.x)),
+              static_cast<float>(std::lround(pos.y)));
+}
+
+} // namespace
+
 GameTown::GameTown() = default;
 
 bool GameTown::Init(int index, const std::string& townPath) {
@@ -96,7 +107,12 @@ void GameTown::AddCharacter(RefPtr<Actor> actor, int areaIndex) {
   if (actor) {
     cameraController_.SetDebugEnabled(false);
     if (areaIndex == -2 && sariaRoomPos_.x >= 0.0f && sariaRoomPos_.y >= 0.0f) {
-      actor->SetPosition(sariaRoomPos_);
+      Vec2 spawnPos = RoundWorldPoint(sariaRoomPos_);
+      if (auto* character = dynamic_cast<CharacterObject*>(actor.Get())) {
+        character->SetCharacterPosition(spawnPos);
+      } else {
+        actor->SetPosition(spawnPos);
+      }
     }
     mapIt->map->AddObject(actor);
     cameraController_.SetFocus(actor->GetPosition());