Fix CodeQL warnings: Replace manual disposal with using declarations

[Copilot]

Pull Request

Description

Resolves 6 CodeQL cs/missed-using-statement warnings in ValidationTests.cs. Replaced manual StringWriter disposal in finally blocks with using declarations.

Before:

StringWriter? outputWriter = null;
try
{
    outputWriter = new StringWriter();
    // ... use outputWriter
}
finally
{
    outputWriter?.Dispose();
}

After:

using var outputWriter = new StringWriter();
try
{
    // ... use outputWriter
}
finally
{
    // automatic disposal at scope end
}

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

CodeQL analysis warnings in test suite.

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 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 '**/*.{yml,yaml}'

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 affect 4 test methods:

• Validation_Run_WithTrxResultsFile_WritesTrxFile
• Validation_Run_WithXmlResultsFile_WritesJUnitFile
• Validation_Run_WithUnsupportedResultsFileExtension_ShowsError
• Validation_Run_WithInvalidResultsFilePath_ShowsError

Net reduction: 16 lines removed. CodeQL alerts: 6 → 0.

Original prompt

Please fix the following CodeQL issues:

test/DemaConsulting.BuildMark.Tests/ValidationTests.cs(46): warning [cs/missed-using-statement] This variable is manually [disposed](1) in a [finally block](2) - consider a C# using statement as a preferable resource management technique.  
test/DemaConsulting.BuildMark.Tests/ValidationTests.cs(47): warning [cs/missed-using-statement] This variable is manually [disposed](1) in a [finally block](2) - consider a C# using statement as a preferable resource management technique.  
test/DemaConsulting.BuildMark.Tests/ValidationTests.cs(106): warning [cs/missed-using-statement] This variable is manually [disposed](1) in a [finally block](2) - consider a C# using statement as a preferable resource management technique.  
test/DemaConsulting.BuildMark.Tests/ValidationTests.cs(107): warning [cs/missed-using-statement] This variable is manually [disposed](1) in a [finally block](2) - consider a C# using statement as a preferable resource management technique.  
test/DemaConsulting.BuildMark.Tests/ValidationTests.cs(166): warning [cs/missed-using-statement] This variable is manually [disposed](1) in a [finally block](2) - consider a C# using statement as a preferable resource management technique.  
test/DemaConsulting.BuildMark.Tests/ValidationTests.cs(211): warning [cs/missed-using-statement] This variable is manually [disposed](1) in a [finally block](2) - consider a C# using statement as a preferable resource management technique.  

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