Group dependabot github-actions updates

[Copilot]

Pull Request

Description

GitHub Actions dependabot updates were creating individual PRs per action. Added groups to the github-actions ecosystem config to batch all updates into a single PR, consistent with the existing NuGet grouping pattern.

groups:
  github-actions-dependencies:
    patterns:
      - "*"

Type of Change

• Code quality improvement

Related Issues

Pre-Submission Checklist

Before submitting this pull request, ensure you have completed the following:

Build and Test

• Code builds successfully: dotnet build --configuration Release
• All unit tests pass: dotnet test --configuration Release
• Code produces zero warnings

Code Quality

• Code formatting is correct: dotnet format --verify-no-changes
• New code has appropriate XML documentation comments
• Static analyzer warnings have been addressed

Quality Checks

Please run the following checks before submitting:

• Spell checker passes: cspell "**/*.{md,cs}"
• Markdown linter passes: markdownlint "**/*.md"
• YAML linter passes: yamllint .

Testing

• Added unit tests for new functionality
• Updated existing tests if behavior changed
• All tests follow the AAA (Arrange, Act, Assert) pattern
• Test coverage is maintained or improved

Documentation

• Updated README.md (if applicable)
• Updated ARCHITECTURE.md (if applicable)
• Added code examples for new features (if applicable)
• Updated requirements.yaml (if applicable)

Additional Notes

Only .github/dependabot.yml is modified — no code, tests, or docs changes required.

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