fix(winappsdk): bump Microsoft.WindowsAppSDK to 1.8.260317003

arcadiog.CompositionExpressions 0.1.3 transitively requires
Microsoft.WindowsAppSDK >= 1.8.260317003, so the older 1.7 PackageReference
in Combobulate.WinAppSdk.csproj triggered NU1605 (package downgrade). Bump
the direct reference and the matching nuspec dependency to the same
version. Also add an explicit arcadiog.CompositionExpressions dependency
on the UWP nuspec target framework group so consumers get the package
on both targets.

Author: arcadiogarcia

Combobulate.nuspec

@@ -11,9 +11,12 @@
     <tags>uwp winui3 winappsdk xaml controls</tags>
     <readme>docs\README.md</readme>
     <dependencies>
-      <group targetFramework="UAP10.0.19041" />
+      <group targetFramework="UAP10.0.19041">
+        <dependency id="arcadiog.CompositionExpressions" version="0.1.3" />
+      </group>
       <group targetFramework="net10.0-windows10.0.19041.0">
-        <dependency id="Microsoft.WindowsAppSDK" version="1.7.250401001" exclude="Build,Analyzers" />
+        <dependency id="Microsoft.WindowsAppSDK" version="1.8.260317003" exclude="Build,Analyzers" />
+        <dependency id="arcadiog.CompositionExpressions" version="0.1.3" />
       </group>
     </dependencies>
   </metadata>

src/Combobulate.WinAppSdk/Combobulate.WinAppSdk.csproj

@@ -21,7 +21,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.7.250401001" />
+    <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.8.260317003" />
     <PackageReference Include="arcadiog.CompositionExpressions" Version="0.1.3" />
     <PackageReference Include="PolySharp" Version="1.14.1">
       <PrivateAssets>all</PrivateAssets>