docs(adapter): lock capability matrix proof surface

[ExplodingUFO]

Summary

• lock the public Avalonia/WPF capability matrix with concrete Supported/Partial rows and explicit fallback guidance
• surface WPF proof markers through CI, release summaries, and prerelease notes
• pin the release-surface contract with demo proof regression tests

Verification

• dotnet test tests/AsterGraph.Demo.Tests/AsterGraph.Demo.Tests.csproj --filter "FullyQualifiedName~DemoProofReleaseSurfaceTests" -nologo -v minimal
• pwsh -File eng/ci.ps1 -Lane contract -Framework all -Configuration Release