Make HierarchyPanel use EventBus for selection changes

- Subscribe to SelectionChangedEvent via EventBus in OnAttach
- Unsubscribe in destructor
- Added m_selectionHandlerId and m_needsRefresh members
- HierarchyPanel now properly receives selection change notifications

editor/src/panels/HierarchyPanel.cpp

@@ -1,6 +1,9 @@
 #include "HierarchyPanel.h"
 #include "Core/IEditorContext.h"
 #include "Core/ISceneManager.h"
+#include "Core/ISelectionManager.h"
+#include "Core/EditorEvents.h"
+#include "Core/EventBus.h"
 #include <XCEngine/Core/Math/Vector3.h>
 #include <XCEngine/Core/Math/Quaternion.h>
 #include <imgui.h>
@@ -13,11 +16,24 @@ HierarchyPanel::HierarchyPanel() : Panel("Hierarchy") {
 }
 
 HierarchyPanel::~HierarchyPanel() {
+    if (m_context) {
+        m_context->GetEventBus().Unsubscribe<SelectionChangedEvent>(m_selectionHandlerId);
+    }
 }
 
 void HierarchyPanel::OnAttach() {
     auto& sceneManager = m_context->GetSceneManager();
     sceneManager.CreateDemoScene();
+    
+    m_selectionHandlerId = m_context->GetEventBus().Subscribe<SelectionChangedEvent>(
+        [this](const SelectionChangedEvent& event) {
+            OnSelectionChanged(event);
+        }
+    );
+}
+
+void HierarchyPanel::OnSelectionChanged(const SelectionChangedEvent& event) {
+    m_needsRefresh = true;
 }
 
 void HierarchyPanel::Render() {