Add opt-in NativeAOT publish path

[Marc-André Moreau (mamoreau-devolutions)]

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Adds an opt-in Windows x64 NativeAOT publish path without changing the existing Release/default publish flow.

Changes:

• Adds Win-x64-NativeAot.pubxml for explicit NativeAOT publishing.
• Adds scripts/publish-nativeaot.ps1 as the repeatable developer entry point.
• Adds CI coverage to publish with the NativeAOT profile and report warnings.
• Updates IPC JSON response writing to use source-generated metadata.
• Documents the experimental NativeAOT workflow.
• Ignores generated artifacts/ output.

Validation:

• dotnet test src\UniGetUI.Windows.slnx --no-restore --verbosity q --nologo /p:Platform=x64 /p:UseSharedCompilation=false /m:1
• pwsh .\scripts\publish-nativeaot.ps1
• Smoke-launched artifacts\nativeaot\win-x64\UniGetUI.exe --help

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Relates to NativeAOT build validation work.