feat: 透明窗口支持 + 退出确认流程 + ImGui 总开关

用户自主改进批次：
- 透明窗口：GLFW_TRANSPARENT_FRAMEBUFFER + 窗口 opacity 0.5，
  swapchain composite alpha 按能力自适应（Opaque/Pre/PostMultiplied），
  Forward 清屏 alpha=0，tonemap 透传 HDR alpha——物体实体、背景透明
- 退出确认：Window 挂 WindowCloseCallback 发事件，App 侧 OnWindowClose
  置确认标记，OnRenderOverlay 弹 ImGui 确认框后 Close()；
  主循环退出条件改为 m_Running（close 事件驱动）
- ImGui 总开关：` 键切换 ImGuiLayer::SetEnabled，禁用时跳过
  NewFrame/OnRenderOverlay/BuildDrawData 整段
- 帧率控制简化：去掉 LimitFps 开关，非 vsync 时恒按 target 限帧
  （默认 60，可调 ≥24）；m_VSync 默认 false（Mailbox 不限速）
- 清理：Model.cpp const 修正，swapchain 日志带 present mode，
  GPU 遥测暂时注释

验证：0 error 0 warning，composite alpha 实测选 PreMultiplied(0x2)，
present=Mailbox

App/main.cpp

@@ -54,8 +54,8 @@ protected:
 
         m_Ground = scene.CreateEntity("Ground");
         m_Ground.AddComponent<TransformComponent>()
-            .SetPosition(glm::vec3(0.0f, -0.5f, 0.0f))
-            .Compose();
+                .SetPosition(glm::vec3(0.0f, -4.5f, 0.0f))
+                .Compose();
         m_Ground.AddComponent<MeshRendererComponent>(MeshRendererComponent{ground});
 
         // 相机实体（primary = 当前渲染视角）
@@ -65,16 +65,17 @@ protected:
         camera.camera.SetPosition(glm::vec3(0.0f, 0.0f, 7.0f));
 
         // 背包实体 × 3（悬浮在地面上方）
-        auto size = 10;
-        for (int i = 0; i < size; ++i) {
-            for (int j = 0 ; j < size; j ++)
+        auto size = 1;
+        for (int i = 0; i < size; ++i)
+        {
+            for (int j = 0; j < size; j++)
             {
                 auto e = scene.CreateEntity("Backpack" + std::to_string(i));
 
                 e.AddComponent<TransformComponent>()
-                    .SetPosition(glm::vec3((i - size * 0.5) * 1.5f, 0.0f, (j - size * 0.5) * 1.5f))
-                    .SetScale(glm::vec3(0.5f))
-                    .Compose();
+                 .SetPosition(glm::vec3((i - size * 0.5) * 1.5f, 0.0f, (j - size * 0.5) * 1.5f))
+                 .SetScale(glm::vec3(0.5f))
+                 .Compose();
 
                 e.AddComponent<MeshRendererComponent>(MeshRendererComponent{backpack});
 
@@ -85,13 +86,17 @@ protected:
         // 灯光实体（第一个灯 = 阴影光源）
         m_KeyLight = scene.CreateEntity("KeyLight");
         m_KeyLight.AddComponent<LightComponent>(
-            LightComponent{glm::vec3(-0.5f, -0.6f, -0.35f),
-                           glm::vec4(1.0f, 0.95f, 0.9f, 1.0f)});
+            LightComponent{
+                glm::vec3(-0.5f, -0.6f, -0.35f),
+                glm::vec4(1.0f, 0.95f, 0.9f, 1.0f)
+            });
 
         scene.CreateEntity("FillLight")
-            .AddComponent<LightComponent>(
-                LightComponent{glm::vec3(0.5f, -0.5f, 0.3f),
-                               glm::vec4(0.3f, 0.5f, 1.0f, 0.8f)});
+             .AddComponent<LightComponent>(
+                 LightComponent{
+                     glm::vec3(0.5f, -0.5f, 0.3f),
+                     glm::vec4(0.3f, 0.5f, 1.0f, 0.8f)
+                 });
     }
 
     void OnUpdate(f32 deltaTime) override
@@ -100,10 +105,11 @@ protected:
 
         // 相机（WASD/Space/Shift 移动）
         m_Camera.GetComponent<CameraComponent>()
-            .camera.Update(GetWindow(), deltaTime);
+                .camera.Update(GetWindow(), deltaTime);
 
         // 旋转动画：编辑 Transform 分量后 Compose 重算 world
-        for (size_t i = 0; i < m_Spinners.size(); ++i) {
+        for (size_t i = 0; i < m_Spinners.size(); ++i)
+        {
             auto& t = m_Spinners[i].GetComponent<TransformComponent>();
             t.rotation.y = m_Time * 60.0f + static_cast<f32>(i) * 40.0f;
             t.scale = glm::vec3(0.5f);
@@ -117,18 +123,18 @@ protected:
 
     void OnRenderOverlay() override
     {
-        if (!m_OverlayVisible) return;
-
         ImGui::ShowDemoWindow();
 
         ImGui::Begin("Scene Debug");
 
         // 阴影光源方向：拖动滑条实时看影子变化
-        if (auto* light = m_KeyLight.TryGetComponent<LightComponent>()) {
+        if (auto* light = m_KeyLight.TryGetComponent<LightComponent>())
+        {
             ImGui::Text("Key Light (shadow caster)");
             ImGui::SliderFloat3("direction",
                                 &light->direction.x, -1.0f, 1.0f);
-            if (ImGui::Button("reset")) {
+            if (ImGui::Button("reset"))
+            {
                 light->direction = glm::vec3(-0.5f, -0.6f, -0.35f);
             }
         }
@@ -138,21 +144,25 @@ protected:
         ImGui::Separator();
         ImGui::Text("Tonemap");
         f32 exposure = renderer.GetExposure();
-        if (ImGui::SliderFloat("exposure", &exposure, 0.1f, 4.0f)) {
+        if (ImGui::SliderFloat("exposure", &exposure, 0.1f, 4.0f))
+        {
             renderer.SetExposure(exposure);
         }
         bool aces = renderer.GetUseACES();
-        if (ImGui::Checkbox("ACES", &aces)) {
+        if (ImGui::Checkbox("ACES", &aces))
+        {
             renderer.SetUseACES(aces);
         }
 
         ImGui::Text("Bloom");
         f32 threshold = renderer.GetBloomThreshold();
-        if (ImGui::SliderFloat("threshold", &threshold, 0.0f, 2.0f)) {
+        if (ImGui::SliderFloat("threshold", &threshold, 0.0f, 2.0f))
+        {
             renderer.SetBloomThreshold(threshold);
         }
         f32 strength = renderer.GetBloomStrength();
-        if (ImGui::SliderFloat("strength", &strength, 0.0f, 2.0f)) {
+        if (ImGui::SliderFloat("strength", &strength, 0.0f, 2.0f))
+        {
             renderer.SetBloomStrength(strength);
         }
 
@@ -161,7 +171,8 @@ protected:
         ImGui::Text("GPU Timings");
         const auto& names = renderer.GetPassNames();
         const auto& times = renderer.GetPassGpuMs();
-        for (size_t i = 0; i < names.size() && i < times.size(); ++i) {
+        for (size_t i = 0; i < names.size() && i < times.size(); ++i)
+        {
             ImGui::Text("  %-12s %.3f ms", names[i].c_str(), times[i]);
         }
 
@@ -170,21 +181,21 @@ protected:
         ImGui::Separator();
         ImGui::Text("Frame");
         bool vsync = app.GetVSync();
-        if (ImGui::Checkbox("VSync", &vsync)) {
+        if (ImGui::Checkbox("VSync", &vsync))
+        {
             app.SetVSync(vsync);
+            if (!vsync)
+            {
+                const f32 target = app.GetTargetFps();
+                app.SetTargetFps(target);
+            }
         }
-        bool limit = app.GetLimitFps();
-        if (ImGui::Checkbox("Limit FPS", &limit)) {
-            app.SetLimitFps(limit);
-        }
-        if (limit) {
-            if (vsync) {
-                ImGui::TextDisabled("(vsync 开启时限帧无效)");
-            } else {
-                f32 target = app.GetTargetFps();
-                if (ImGui::SliderFloat("target fps", &target, 24.0f, 360.0f, "%.0f")) {
-                    app.SetTargetFps(target);
-                }
+        if (!vsync)
+        {
+            f32 target = app.GetTargetFps();
+            if (ImGui::SliderFloat("target fps", &target, 24.0f, 360.0f, "%.0f"))
+            {
+                app.SetTargetFps(target);
             }
         }
 
@@ -194,32 +205,76 @@ protected:
                     static_cast<unsigned long long>(GetFrameCount()));
 
         ImGui::End();
+
+
+        // 自定义重载事件： 重载关闭事件模态框
+        {
+            if (m_ShowQuitConfirm)
+            {
+                ImGui::OpenPopup("Should quit?");
+                m_ShowQuitConfirm = false;
+            }
+
+            ImGui::SetNextWindowPos(
+                ImGui::GetMainViewport()->GetCenter(),
+                ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
+
+            if (ImGui::BeginPopupModal("Should quit?", nullptr,
+                                       ImGuiWindowFlags_AlwaysAutoResize))
+            {
+                ImGui::TextUnformatted("Quit the application?");
+                ImGui::Separator();
+                if (ImGui::Button("Yes", ImVec2(120, 0)))
+                {
+                    m_QuitConfirmed = true;
+                    ImGui::CloseCurrentPopup();
+                }
+                ImGui::SameLine();
+                if (ImGui::Button("No", ImVec2(120, 0)))
+                {
+                    ImGui::CloseCurrentPopup();
+                }
+                ImGui::EndPopup();
+            }
+
+            if (m_QuitConfirmed)
+            {
+                m_QuitConfirmed = false;
+                Close();
+            }
+        }
+    }
+
+    void OnWindowClose(const Event& event) override
+    {
+        m_ShowQuitConfirm = true;
     }
 
     void OnKeyPress(const Event& event) override
     {
-        if (event.key == GLFW_KEY_GRAVE_ACCENT) {
-            m_OverlayVisible = !m_OverlayVisible;   // ` 反折叠加层
+        if (event.key == GLFW_KEY_GRAVE_ACCENT)
+        {
+            SetImGuiEnabled(!GetImGuiEnabled());
         }
-        if (event.key == GLFW_KEY_F1) {
+        if (event.key == GLFW_KEY_F1)
+        {
             STATS.PrintComparison();
         }
-        if (event.key == GLFW_KEY_ESCAPE) {
-            Close();
-        }
     }
 
+
     void OnWindowResize(const Event& event) override
     {
         ENGINE_INFO("App: window resized to {}x{}", event.width, event.height);
     }
 
 private:
-    EntityHandle m_Camera{};                 // Scene::CreateEntity 之前为空
+    bool m_ShowQuitConfirm = false;
+    bool m_QuitConfirmed = false;
+    EntityHandle m_Camera{}; // Scene::CreateEntity 之前为空
     EntityHandle m_Ground{};
     EntityHandle m_KeyLight{};
     std::vector<EntityHandle> m_Spinners;
-    bool m_OverlayVisible = true;
     f32 m_Time = 0.0f;
 };
 
@@ -227,10 +282,12 @@ int main()
 {
     SandboxApp app;
 
-    try {
+    try
+    {
         app.Run();
     }
-    catch (const std::exception& e) {
+    catch (const std::exception& e)
+    {
         ENGINE_FATAL("Exception: {}", e.what());
         return -1;
     }