MainWindowViewTests kept failing on CI in Test Case Cleanup ('The calling
thread cannot access this object') while passing 56/56 locally. The cause was
delivery, not the fix: xunit.runner.json only takes effect if it is copied
beside the test DLL, and under CI's 'dotnet build' + 'dotnet test --no-build'
split it did not arrive, so CI ran with parallel collections while local runs
did not.
[assembly: CollectionBehavior(DisableTestParallelization = true)] is compiled
into the DLL and cannot fail to deploy. It lives beside the existing
AvaloniaTestApplication/AvaloniaTestIsolation attributes, which document the
same thread-affinity hazard. The json and its csproj copy rule are removed so
there is one source of truth.
45f88d2d18