Fix Windows SDK projection smoke tests after projection target split

PR #2487 split the projection target: the "Windows Metadata not provided
or detected" check moved out of CsWinRTGenerateProjection into a new
private _CsWinRTComputeProjectionRefGenInputs target, which runs as a
dependency of CsWinRTGenerateProjection. MSBuild runs a target's
DependsOnTargets before its BeforeTargets hooks, so the smoke tests'
_StageWindowsSdkContractsInputs target (BeforeTargets=CsWinRTGenerateProjection)
now added the SDK winmds to @(CsWinRTInputs) *after* the check had already
run against an empty list and failed.

Feed the SDK contract winmds into @(CsWinRTInputs) via a static,
evaluation-time ItemGroup instead of a target, matching how every in-repo
projection project (src/Projections/*, Projection/Projection.csproj) does
it. This makes the inputs independent of how the CsWinRT projection
targets are factored. NuGetPackageRoot and the restored winmds are both
available at evaluation time (the smoke tests always run a full build,
which restores first). The folder-existence diagnostic is kept in a small
target anchored to the standard PrepareForBuild target so it stays
ordering-independent.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 435af478-1759-4c7e-8176-3b92f72136ec

Author: Sergio0694

src/Tests/SmokeTests/WindowsSdkContracts.targets

@@ -28,29 +28,41 @@
   </ItemGroup>
 
   <!--
-    Stage the SDK '.winmd' files as projection inputs before the reference projection generator runs.
-    The metadata lives in the downloaded package's 'ref/netstandard2.0' folder. We exclude the union
-    'Windows.winmd' (it would duplicate every contract) and the handful of contracts that the desktop
-    'Microsoft.Windows.SDK.NET.Ref' package omits (phone/embedded/etc.), matching the official Windows
-    SDK projection build in 'WinRT.Sdk.Projection.csproj'.
+    Stage the SDK '.winmd' files as projection inputs. The metadata lives in the downloaded package's
+    'ref/netstandard2.0' folder. We exclude the union 'Windows.winmd' (it would duplicate every contract)
+    and the handful of contracts that the desktop 'Microsoft.Windows.SDK.NET.Ref' package omits
+    (phone/embedded/etc.), matching the official Windows SDK projection build in 'WinRT.Sdk.Projection.csproj'.
+
+    These inputs are added statically (at evaluation time), exactly like the in-repo projection projects
+    feed '@(CsWinRTInputs)' (e.g. 'src/Projections/*/*.csproj' and the sibling 'Projection/Projection.csproj').
+    Doing it statically instead of from a target keeps the inputs in place regardless of how the CsWinRT
+    projection targets are factored: the 'Windows Metadata not provided or detected' check now runs in a
+    private '_CsWinRTComputeProjectionRefGenInputs' target (a dependency of 'CsWinRTGenerateProjection'), so
+    a 'BeforeTargets="CsWinRTGenerateProjection"' hook would add these inputs *after* that check has already
+    run and failed. 'NuGetPackageRoot' and the restored '.winmd' files are both available at evaluation time
+    (the smoke tests always run a full 'dotnet build', which restores first).
   -->
-  <Target Name="_StageWindowsSdkContractsInputs" BeforeTargets="CsWinRTGenerateProjection">
+  <PropertyGroup>
+    <_SdkContractsWinMDFolder>$([MSBuild]::NormalizeDirectory('$(NuGetPackageRoot)', '$(_SdkContractsPackageName)', '$(_SdkContractsPackageVersion)', 'ref', 'netstandard2.0'))</_SdkContractsWinMDFolder>
+  </PropertyGroup>
 
-    <PropertyGroup>
-      <_SdkContractsWinMDFolder>$([MSBuild]::NormalizeDirectory('$(NuGetPackageRoot)', '$(_SdkContractsPackageName)', '$(_SdkContractsPackageVersion)', 'ref', 'netstandard2.0'))</_SdkContractsWinMDFolder>
-    </PropertyGroup>
+  <ItemGroup>
+    <CsWinRTInputs Include="$(_SdkContractsWinMDFolder)*.winmd"
+                   Exclude="$(_SdkContractsWinMDFolder)Windows.winmd;
+                            $(_SdkContractsWinMDFolder)Windows.Embedded.DeviceLockdown.DeviceLockdownContract.winmd;
+                            $(_SdkContractsWinMDFolder)Windows.Networking.NetworkOperators.NetworkOperatorsFdnContract.winmd;
+                            $(_SdkContractsWinMDFolder)Windows.Phone.PhoneContract.winmd;
+                            $(_SdkContractsWinMDFolder)Windows.Phone.StartScreen.DualSimTileContract.winmd;
+                            $(_SdkContractsWinMDFolder)Windows.UI.WebUI.Core.WebUICommandBarContract.winmd" />
+  </ItemGroup>
 
+  <!--
+    Fail fast with a targeted message if the SDK metadata didn't restore, before the projection generator
+    reports the generic 'Windows Metadata not provided or detected' error. Anchored to the standard
+    'PrepareForBuild' target (not a CsWinRT-internal one) so it stays independent of target ordering.
+  -->
+  <Target Name="_ValidateWindowsSdkContractsInputs" BeforeTargets="PrepareForBuild">
     <Error Condition="!Exists('$(_SdkContractsWinMDFolder)')"
            Text="Windows SDK metadata folder not found at '$(_SdkContractsWinMDFolder)'. Check that the PackageDownload for $(_SdkContractsPackageName) $(_SdkContractsPackageVersion) succeeded." />
-
-    <ItemGroup>
-      <CsWinRTInputs Include="$(_SdkContractsWinMDFolder)*.winmd"
-                     Exclude="$(_SdkContractsWinMDFolder)Windows.winmd;
-                              $(_SdkContractsWinMDFolder)Windows.Embedded.DeviceLockdown.DeviceLockdownContract.winmd;
-                              $(_SdkContractsWinMDFolder)Windows.Networking.NetworkOperators.NetworkOperatorsFdnContract.winmd;
-                              $(_SdkContractsWinMDFolder)Windows.Phone.PhoneContract.winmd;
-                              $(_SdkContractsWinMDFolder)Windows.Phone.StartScreen.DualSimTileContract.winmd;
-                              $(_SdkContractsWinMDFolder)Windows.UI.WebUI.Core.WebUICommandBarContract.winmd" />
-    </ItemGroup>
   </Target>
 </Project>