Restore duplicate QuirkSettings.h include and GetEnableFabric function as requested

Co-authored-by: anupriya13 <54227869+anupriya13@users.noreply.github.com>

Author: Copilot

vnext/Microsoft.ReactNative/QuirkSettings.cpp

@@ -5,6 +5,7 @@
 #include "QuirkSettings.h"
 #include "QuirkSettings.g.cpp"
 
+#include "QuirkSettings.h"
 #include "React.h"
 #include "ReactPropertyBag.h"
 
@@ -88,6 +89,11 @@ winrt::Microsoft::ReactNative::ReactPropertyId<bool> EnableSyncDetachRootViewPro
   return propId;
 }
 
+winrt::Microsoft::ReactNative::ReactPropertyId<bool> EnableFabricProperty() noexcept {
+  static winrt::Microsoft::ReactNative::ReactPropertyId<bool> propId{L"ReactNative.QuirkSettings", L"EnableFabric"};
+  return propId;
+}
+
 #pragma region IDL interface
 
 /*static*/ void QuirkSettings::SetMatchAndroidAndIOSStretchBehavior(
@@ -174,4 +180,8 @@ winrt::Microsoft::ReactNative::ReactPropertyId<bool> EnableSyncDetachRootViewPro
   return properties.Get(EnableSyncDetachRootViewProperty()).value_or(false);
 }
 
+/*static*/ bool QuirkSettings::GetEnableFabric(ReactPropertyBag properties) noexcept {
+  return properties.Get(EnableFabricProperty()).value_or(false);
+}
+
 } // namespace winrt::Microsoft::ReactNative::implementation

vnext/Microsoft.ReactNative/QuirkSettings.h

@@ -31,6 +31,8 @@ struct QuirkSettings : QuirkSettingsT<QuirkSettings> {
   static bool GetSuppressWindowFocusOnViewFocus(winrt::Microsoft::ReactNative::ReactPropertyBag properties) noexcept;
   static bool GetUseRuntimeScheduler(winrt::Microsoft::ReactNative::ReactPropertyBag properties) noexcept;
 
+  static bool GetEnableFabric(winrt::Microsoft::ReactNative::ReactPropertyBag properties) noexcept;
+
   static void SetMapWindowDeactivatedToAppStateInactive(
       winrt::Microsoft::ReactNative::ReactPropertyBag properties,
       bool value) noexcept;