Add .NET 9.0.X SDK support to GitHub Actions workflows

[Copilot]

GitHub Actions workflows need to support the .NET 9.0.X SDK. The two workflows require different approaches based on whether they manage single or multiple SDK versions.

Changes

• dotnet-core.yml — Adds a new setup-dotnet step for 9.0.x with include-prerelease: true, following the same pattern as existing 6.x–8.x entries:

  - name: 🔨 Use .NET 9.0.X SDK
    uses: actions/setup-dotnet@v1
    with:
      dotnet-version: '9.0.x'
      include-prerelease: true

• publish.yml — Updates the single SDK setup from 8.0.x to 9.0.x (retains existing include-prerelease: true).

Original prompt

Update all GitHub Actions workflow files in .github/workflows to support .NET 9.0.X SDK. For workflows with multiple SDK setups (like dotnet-core.yml), add a new step to setup .NET 9.0.X with include-prerelease: true. For workflows with a single SDK setup (like publish.yml), update the existing setup to use .NET 9.0.X with include-prerelease: true.

This pull request was created from Copilot chat.

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