Editor: rework default layout to UE5 arrangement

Panels renamed to UE semantics (docking identity change): Hierarchy ->
Outliner, Inspector -> Details, Asset Browser -> Content Browser.

Default DockBuilder layout now matches UE5 factory layout: Details
docked right (full height), Content Browser docked bottom spanning
left+center, Outliner top-left, Viewport center with Stats as a
side tab.

Legacy imgui.ini (old window names, no new names) is removed once at
Init so the new default rebuilds cleanly; fresh or new-style ini is
untouched.

App/editor/InspectorPanel.cpp

@@ -154,7 +154,7 @@ namespace
 
 void InspectorPanel::Draw(const EditorContext& ctx, entt::entity selected)
 {
-    ImGui::Begin("Inspector");
+    ImGui::Begin("Details");
 
     auto& reg = ctx.scene->GetRegistry();
     if (selected == entt::null || !reg.valid(selected))