fix: ImGui hover jumps while cursor captured (RMB look / MMB orbit)

With GLFW_CURSOR_DISABLED the official GLFW backend keeps feeding
virtual unbounded cursor coords to ImGui each frame, so hover state
wanders across hidden panels while the physical cursor is invisible.
Append a "mouse left the window" pos event before ImGui::NewFrame
whenever the cursor is captured - ImGui treats the frame as mouseless.

Engine/include/Engine/ImGui/ImGuiLayer.h

@@ -68,6 +68,7 @@ namespace Engine {
         // 生命周期保证：Application 成员序中 ImGuiLayer 在 Renderer 之后声明
         //（先析构），因此 Device 引用在整个层生命周期内有效
         Device& m_Device;
+        Window& m_Window;   // 光标捕获状态查询（NewFrame hover 门控）
         vk::DescriptorPool m_Pool;
         bool m_Enabled = true;
         ImTextureID m_SceneTextures[kMaxFramesInFlight]{};

Engine/src/ImGui/ImGuiLayer.cpp

@@ -24,7 +24,7 @@ namespace Engine {
     }
 
     ImGuiLayer::ImGuiLayer(Window& window, Renderer& renderer)
-        : m_Device(renderer.GetDevice())
+        : m_Device(renderer.GetDevice()), m_Window(window)
     {
         Device& device = renderer.GetDevice();
 
@@ -133,6 +133,13 @@ namespace Engine {
     {
         ImGui_ImplVulkan_NewFrame();
         ImGui_ImplGlfw_NewFrame();
+        // 光标捕获期间（RMB 自由视角 / MMB 环绕，GLFW_CURSOR_DISABLED），
+        // 官方后端每帧喂的虚拟无界坐标没有屏幕语义——hover 会随移动在
+        // 面板间乱窜（"鼠标被隐藏但 UI 被 hover"）。在 NewFrame 处理
+        // 事件前追加"鼠标离开"事件清空 hover，ImGui 本帧视为无鼠标
+        if (m_Window.IsCursorCaptured()) {
+            ImGui::GetIO().AddMousePosEvent(-FLT_MAX, -FLT_MAX);
+        }
         ImGui::NewFrame();
     }