fix(slnx): add platform mappings for JitHub.WinUI.Tests project

Map ARM/Any CPU solution platforms to the project's actual configurations
(x86/x64/ARM64) to prevent the 'configuration does not exist' warning.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Xueyang-Song

JitHub.slnx

@@ -20,5 +20,12 @@
     <Deploy Solution="*|x86" />
     <Deploy Solution="Debug|Any CPU" />
   </Project>
-  <Project Path="JitHub.WinUI.Tests/JitHub.WinUI.Tests.csproj" />
+  <Project Path="JitHub.WinUI.Tests/JitHub.WinUI.Tests.csproj">
+    <Platform Solution="*|ARM" Project="x86" />
+    <Platform Solution="*|ARM64" Project="ARM64" />
+    <Platform Solution="*|x64" Project="x64" />
+    <Platform Solution="*|x86" Project="x86" />
+    <Platform Solution="Debug|Any CPU" Project="x64" />
+    <Platform Solution="Release|Any CPU" Project="x86" />
+  </Project>
 </Solution>