CI: update NuGet publish workflow to current action majors and default MSBuild toolchain

[Copilot]

The NuGet publish workflow was selecting a VS preview toolchain (vs-version: [18.0,19.0)) that no longer aligns with the hosted runner image, causing MSB8020 for projects targeting v143. This PR updates the workflow to current action majors and removes the brittle Visual Studio version assumption while preserving the existing build/package flow and matrix.

• Toolchain selection hardening

  • Upgraded microsoft/setup-msbuild from v1.0.2 to v2.
  • Removed explicit vs-version pin so MSBuild resolves from the default windows-latest environment.

• Action version refresh

  • Upgraded actions/checkout from v3 to v4 in both build and package jobs.

• Script execution consistency

  • Added explicit shell: pwsh to PowerShell-based script steps in the package job.

• Build/package behavior preserved

  • Kept runs-on: windows-latest.
  • Kept matrix coverage unchanged: Release, Debug × x64, x86, ARM64.
  • Kept artifact packaging/publish flow intact.

- name: Add MSBuild to PATH
  uses: microsoft/setup-msbuild@v2
  # removed:
  # with:
  #   vs-version: '[18.0,19.0)'