Pin Microsoft.Build.Tasks.Git to 10.0.401 via central package management

[Copilot]

Builds were failing with NU1902 (warnings treated as errors) due to a vulnerable Microsoft.Build.Tasks.Git resolution path. This change remediates the dependency graph at the central package-management layer to force a non-vulnerable version.

• Central vulnerability remediation

  • Added an explicit central PackageVersion for Microsoft.Build.Tasks.Git.
  • Set version to 10.0.401 (safe baseline called out in the issue context).

• Version coherence for SourceLink stack

  • Introduced a shared SourceLinkVersion property in Directory.Packages.props.
  • Bound both Microsoft.Build.Tasks.Git and Microsoft.SourceLink.GitHub to the same property to prevent drift in future updates.

• Scope

  • Changes are limited to Directory.Packages.props; no project-level package references were modified.

<PropertyGroup>
  <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
  <CentralPackageTransitivePinningEnabled>true</CentralPackageTransitivePinningEnabled>
  <SourceLinkVersion>10.0.401</SourceLinkVersion>
</PropertyGroup>

<ItemGroup>
  <PackageVersion Include="Microsoft.Build.Tasks.Git" Version="$(SourceLinkVersion)" />
  <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="$(SourceLinkVersion)" />
</ItemGroup>