Sync with TemplateDotNetTool template (PRs #39–#45)

[Copilot]

Pull Request

Description

Applies consistency updates from TemplateDotNetTool template PRs #39–#45.

GitHub Actions

• upload-artifact v6 → v7, download-artifact v7 → v8 (build.yaml, release.yaml)
• Add groups block for github-actions-dependencies in dependabot.yml (mirrors existing NuGet grouping)

NuGet Packages

• SonarAnalyzer.CSharp 10.19 → 10.20 (7 false-positive fixes, S2068/S6418 promoted to Vulnerability)
• Microsoft.NET.Test.Sdk 18.0.1 → 18.3.0
• Add Polyfill 9.12.0 (source-only, zero runtime footprint) to main csproj

Code Quality

• LangVersion 12 → latest in both csproj files
• GenerateDocumentationFile True → true (boolean casing consistency)
• Add ArgumentNullException.ThrowIfNull null guards to Context.Create(), ArgumentParser.ParseArguments(), and Validation.Run()
• Add explanatory comments for PrivateAssets/IncludeAssets pattern in main csproj

Agent / Docs

• Add Assert.StartsWith anti-pattern ([Feature]: Version Capture #5) to test-developer.md
• Add CLA sentence to README.md License section

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• 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
• Self-validation tests pass:
  dotnet run --project src/DemaConsulting.VersionMark --configuration Release --framework net10.0
--no-build -- --validate
• 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

Changes are purely additive/upgrades with no behavioral impact on tool functionality. All 103 unit tests pass with 0 warnings and 0 CodeQL alerts.

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