Align Avalonia desktop and headless package lines for CI stability

The latest CI failures were no longer in the CLI workflow checks; they
had moved into Avalonia-based automation and NuGet smoke paths. The
common failure signature was a TypeLoadException for
`Avalonia.Compatibility.OperatingSystemEx` or a missing
`Avalonia.Rendering.IRenderLoop`, both pointing to mixed Avalonia
package lines across test hosts.

This change aligns the desktop/headless/HarfBuzz/diagnostics package
versions onto the 12.0.0-rc1 line so headless automation and
UsePlatformDetect-based smoke flows load a consistent Avalonia stack.

Constraint: Preserve the existing automation harness and smoke-test structure while fixing the package-line mismatch underneath
Constraint: Keep the change minimal and focused on the proven Avalonia version skew instead of broad unrelated dependency churn
Rejected: Patch the Avalonia headless fixture implementation directly | the root cause was package incompatibility, not harness control flow
Rejected: Skip failing automation/smoke jobs in CI | would mask a real platform regression instead of restoring intended coverage
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep Avalonia core, desktop, headless, theme, font, and HarfBuzz package lines aligned across test hosts to avoid startup type-load failures
Tested: `dotnet test tests/Agibuild.Fulora.Integration.Tests.Automation/Agibuild.Fulora.Integration.Tests.Automation.csproj --configuration Release -v minimal` (209 passed)
Tested: `dotnet run --project tests/Agibuild.Fulora.Integration.NugetPackageTests/Agibuild.Fulora.Integration.NugetPackageTests.csproj --configuration Release --no-restore -- --smoke-test` (all 7 smoke steps passed)
Tested: `dotnet test tests/Agibuild.Fulora.UnitTests/Agibuild.Fulora.UnitTests.csproj --configuration Release -v minimal` (2177 passed)
Not-tested: Fresh GitHub Actions status for this package-alignment follow-up until remote CI completes
Related: 7ad6821

Author: Hongwei-MB

Directory.Packages.props

@@ -8,11 +8,11 @@
     <PackageVersion Include="Avalonia" Version="12.0.0-rc1" />
     <PackageVersion Include="Avalonia.Android" Version="12.0.0-preview2" />
     <PackageVersion Include="Avalonia.Browser" Version="12.0.0-preview2" />
-    <PackageVersion Include="Avalonia.Desktop" Version="12.0.0-preview2" />
-    <PackageVersion Include="Avalonia.Diagnostics" Version="12.0.0-preview2" />
+    <PackageVersion Include="Avalonia.Desktop" Version="12.0.0-rc1" />
+    <PackageVersion Include="Avalonia.Diagnostics" Version="12.0.0-rc1" />
     <PackageVersion Include="Avalonia.Fonts.Inter" Version="12.0.0-rc1" />
-    <PackageVersion Include="Avalonia.HarfBuzz" Version="12.0.0-preview2" />
-    <PackageVersion Include="Avalonia.Headless" Version="12.0.0-preview2" />
+    <PackageVersion Include="Avalonia.HarfBuzz" Version="12.0.0-rc1" />
+    <PackageVersion Include="Avalonia.Headless" Version="12.0.0-rc1" />
     <PackageVersion Include="Avalonia.iOS" Version="12.0.0-preview2" />
     <PackageVersion Include="Avalonia.Themes.Fluent" Version="12.0.0-rc1" />
   </ItemGroup>
@@ -74,4 +74,4 @@
     <PackageVersion Include="Nuke.Common" Version="10.1.0" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="11.0.100-preview.2.26159.112" />
   </ItemGroup>
-</Project>
+</Project>

tests/Agibuild.Fulora.Integration.Tests.Automation/Agibuild.Fulora.Integration.Tests.Automation.csproj

@@ -18,8 +18,8 @@
 
   <ItemGroup>
     <PackageReference Include="Avalonia.Fonts.Inter" />
-    <PackageReference Include="Avalonia.HarfBuzz" VersionOverride="12.0.0-rc1" />
-    <PackageReference Include="Avalonia.Headless" VersionOverride="12.0.0-rc1" />
+    <PackageReference Include="Avalonia.HarfBuzz" />
+    <PackageReference Include="Avalonia.Headless" />
     <PackageReference Include="Avalonia.Themes.Fluent" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
     <PackageReference Include="xunit.v3" />