Fixes #5248. Expand AOT smoke coverage to Windows and explicit clone paths

[Copilot]

Proposed Changes/Todos

The PR now validates NativeAOT in the failure mode that previously escaped: runtime execution on Windows, not just Linux publish. It also makes the smoke test directly execute the dictionary deep-clone surfaces that have regressed in AOT before.

• CI: run AOT publish-and-run smoke test on both OSes

  • build-validation now runs on an OS matrix: ubuntu-latest, windows-latest
  • Smoke execution is platform-specific (NativeAot on Linux, NativeAot.exe on Windows)

• NativeAot smoke path: explicit dictionary clone coverage

  • In --smoke-test, added direct DeepCloner.DeepClone (...) calls for:
    • Color.Colors16
    • Application.DefaultKeyBindings
    • View.DefaultKeyBindings
    • View.ViewKeyBindings
    • ThemeManager.Themes
    • SchemeManager.Schemes
  • Keeps existing full app lifecycle smoke run intact

• Workflow hardening

  • Added explicit workflow token permissions: contents: read

• Example (new explicit clone coverage)

private static void ExerciseDictionaryDeepCloning ()
{
    _ = DeepCloner.DeepClone (Color.Colors16);
    _ = DeepCloner.DeepClone (Application.DefaultKeyBindings);
    _ = DeepCloner.DeepClone (View.DefaultKeyBindings);
    _ = DeepCloner.DeepClone (View.ViewKeyBindings);
    _ = DeepCloner.DeepClone (ThemeManager.Themes);
    _ = DeepCloner.DeepClone (SchemeManager.Schemes);
}

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