Add package testing for .NET 8, 9, and 10 on Windows

[Copilot]

The NuGet package was not being tested after build to verify the packaged Weasyprint tool executes correctly.

Changes

• build.yaml: Added test job that matrix-tests the built NuGet package on Windows with .NET 8.x, 9.x, and 10.x

  • Downloads build artifacts
  • Installs package globally via dotnet tool install
  • Executes weasyprint --help and validates exit code

• AGENTS.md: Updated build process documentation to include test job validation

• CONTRIBUTING.md: Updated CI pipeline documentation to reflect automated package testing

Example

The test job runs after successful build:

test:
  name: Test Package
  needs: build
  runs-on: windows-latest
  strategy:
    matrix:
      dotnet-version: ['8.x', '9.x', '10.x']
  steps:
    - name: Setup dotnet
      uses: actions/setup-dotnet@v5
      with:
        dotnet-version: ${{ matrix.dotnet-version }}
    
    - name: Download Artifacts
      uses: actions/download-artifact@v6
      with:
        name: build-artifacts
        path: artifacts
    
    - name: Install Package
      shell: pwsh
      run: |
        dotnet tool install --global --add-source artifacts DemaConsulting.WeasyprintTool
    
    - name: Test Weasyprint Tool
      shell: pwsh
      run: |
        weasyprint --help
        if ($LASTEXITCODE -ne 0) {
          Write-Error "Weasyprint tool failed with exit code $LASTEXITCODE"
          exit 1
        }

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Feature]: Add package testing</issue_title>
<issue_description>### Problem Statement

After building the package, it should be tested to ensure the packaged Weasyprint tool executes correctly.

Proposed Solution

The build.yaml file should be updated to:

Add a test job which matrix-tests on Windows with DotNet 8, 9, and 10 by downloading the NuGet package created in the build job, installing it, and then running the weasyprint tool with a simple command line such as asking for help and then checking the tool ran without error.

The CI testing information should be updated in the AGENTS.md and CONTRIBUTING.md files.

Alternatives Considered

No response

Additional Context

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature]: Add package testing #10

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