Add a smaller .NET 10 release package

[stuartd]

What changed

• publish a second win-x64-net10 single-file package for machines with the x64 .NET 10 Desktop Runtime
• retain the existing self-contained package as win-x64-self-contained
• validate both folders and ZIPs contain exactly ClipDiff.exe and ClipDiff.ShellExtension.dll
• upload both variants from CI and attach both ZIPs to tagged GitHub releases
• document how to choose between them and verify Microsoft.WindowsDesktop.App 10.x

Result

The application layout remains two files for both variants. In the successful Windows workflow, the GitHub Actions artifacts were approximately:

• self-contained: 77.9 MB compressed
• .NET 10-dependent: 6.8 MB compressed

Verification

Windows build succeeded, including native tests, .NET tests, both publish modes, package validation, and both artifact uploads.