feat(desktop): add generic operator verification flows

[PrzemyslawKlys]

Summary

• add generic operator verification primitives for modern Windows surfaces, including visual baselines, OCR text anchors, and visual-change verification
• expand the DesktopManager test harnesses and live certification suites across classic controls, hosted WPF, WebView2, and WinUI surfaces
• add a public Windows verification plugin scaffold and supporting docs/scripts for MCP-driven inspect -> act -> verify workflows

Testing

• dotnet build C:\Support\GitHub\DesktopManager\Sources\DesktopManager.Tests\DesktopManager.Tests.csproj -c Debug -f net8.0-windows10.0.19041.0
• dotnet test C:\Support\GitHub\DesktopManager\Sources\DesktopManager.Tests\DesktopManager.Tests.csproj -c Debug -f net8.0-windows10.0.19041.0 --filter "FullyQualifiedNameScreenshotServiceTests|FullyQualifiedNameMcpCatalogTests|FullyQualifiedNameMcpServerTests|FullyQualifiedNameDesktopManagerAutomationBasicsTests"
• dotnet test C:\Support\GitHub\DesktopManager\Sources\DesktopManager.Tests\DesktopManager.Tests.csproj -c Debug -f net8.0-windows10.0.19041.0 --filter "FullyQualifiedName~DesktopManagerAutomationBasicsTests"