Cmdpal: Fix cmdpal toolkit restore failure for slnx in release pipeline

[vanzue]

Summary of the Pull Request

Error from pipeline:

Invalid input 'PowerToys.slnx'. The file type was not recognized.
MSBuild version 17.14.23+b0019275e for .NET Framework
Build started 12/8/2025 6:33:14 AM.

Nuget support for slnx will be ready in nuget version 7, so use msbuild to restore

PR Checklist

• Closes: #xxx

• Communication: I've discussed this with core contributors already. If the work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end-user-facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR fixes a pipeline build failure in the Command Palette SDK build script by switching from nuget.exe restore to MSBuild-based restore for the PowerToys.slnx solution file. NuGet version 6 doesn't recognize the .slnx file format, which will be supported in NuGet version 7. Additionally, the Microsoft.Windows.SDK.BuildTools package version is updated to 10.0.26100.6901 to align with the version already specified in Directory.Packages.props.

Key changes:

• Replace nuget.exe restore with msbuild.exe /t:restore /p:RestorePackagesConfig=true for .slnx compatibility
• Update Microsoft.Windows.SDK.BuildTools from version 10.0.26100.4188 to 10.0.26100.6901 across packages.config and project files

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/modules/cmdpal/extensionsdk/nuget/BuildSDKHelper.ps1	Replaced nuget restore with MSBuild restore command for .slnx solution; added $solutionPath variable
src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions/packages.config	Updated Microsoft.Windows.SDK.BuildTools version to align with repo-wide version
src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions/Microsoft.CommandPalette.Extensions.vcxproj	Updated WindowsSdkBuildToolsNuget path to reference new SDK version

[Copilot]

The target name should use lowercase /t:restore to match the established pattern used consistently throughout the codebase (see tools/build/build-common.ps1:90 and tools/build/build-installer.ps1:144). While MSBuild target names are case-insensitive, following the existing convention improves code consistency.

Suggested change:

"/t:restore"

Suggested change

	"/t:Restore"
	"/t:restore"

[Copilot]

The MSBuild restore command should check $LASTEXITCODE and exit on failure, following the pattern used in tools/build/build-common.ps1:71-75. Without this check, if the restore fails, the script will continue to the build step, potentially causing confusing downstream errors.

Suggested addition after line 65:

if ($LASTEXITCODE -ne 0) {
  Write-Error "NuGet restore failed for $solutionPath"
  Exit $LASTEXITCODE
}

Suggested change

	& $msbuildPath $restoreArgs
	& $msbuildPath $restoreArgs
	if ($LASTEXITCODE -ne 0) {
	Write-Error "NuGet restore failed for $solutionPath"
	Exit $LASTEXITCODE
	}