Fix CodeQL warnings: LINQ optimizations and resource disposal

[Copilot]

Pull Request

Description

Resolves 18 CodeQL warnings: 7 LINQ inefficiencies in source code and 11 resource disposal issues in tests.

LINQ Optimizations (Source)

Replaced imperative loops with declarative LINQ where CodeQL flagged implicit filtering/mapping:

• FindRequirement: foreach → .FirstOrDefault() for search-and-return pattern
• AllRequirementTestsPassed: foreach with early return → .Select().All()
• GetRequirementTestStats: foreach → .Select() for mapping test names to results
• CollectTestNames: nested loops → .SelectMany() and .Select()
• CollectAllTests: foreach → .Select().Where() for mapping and filtering child requirements

Resource Disposal (Tests)

All StringWriter instances now properly disposed:

// Before: leaked resources
var output = new StringWriter();
Console.SetOut(output);

// After: guaranteed disposal
using var output = new StringWriter();
Console.SetOut(output);

Replaced manual try-finally disposal in Context_Dispose_WithLogFile_ClosesLogFile with using statement for proper resource management.

Type of Change

• Code quality improvement

Related Issues

Pre-Submission Checklist

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

• 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

CodeQL analysis now reports 0 alerts. All 109 tests pass. No functional changes - semantics preserved.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature]: CodeQL Cleanup</issue_title>
<issue_description>### Problem Statement

CodeQL is reporting numerous findings

Proposed Solution

Please review and fix the following findings:

src/DemaConsulting.ReqStream/TraceMatrix.cs(271): warning [cs/linq/missed-where] This foreach loop [implicitly filters its target sequence](1) - consider filtering the sequence explicitly using '.Where(...)'.  
src/DemaConsulting.ReqStream/Requirements.cs(219): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
src/DemaConsulting.ReqStream/TraceMatrix.cs(225): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
src/DemaConsulting.ReqStream/TraceMatrix.cs(252): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
src/DemaConsulting.ReqStream/TraceMatrix.cs(280): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
src/DemaConsulting.ReqStream/TraceMatrix.cs(359): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
src/DemaConsulting.ReqStream/TraceMatrix.cs(465): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
test/DemaConsulting.ReqStream.Tests/ProgramTests.cs(60): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ProgramTests.cs(87): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(394): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(417): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(440): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(464): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ProgramTests.cs(352): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ProgramTests.cs(379): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(508): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ProgramTests.cs(487): warning [cs/local-not-disposed] Disposable 'StringWriter' is created but not disposed.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(658): warning [cs/dispose-not-called-on-throw] Dispose missed if exception is thrown by [call to method WriteLine](1).  

Alternatives Considered

No response

Usage Examples

Benefits

Code Quality

Priority

Low - Nice to have

Willingness to Contribute

Yes, I can submit a pull request

Additional Context

No response

Checklist

• I have searched existing issues to ensure this is not a duplicate
• I have provided a clear description of the feature
• I have explained why this feature would be useful</issue_description>

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

• Fixes [Feature]: CodeQL Cleanup #85

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[Malcolmnixon]

@copilot I'm still seeing the following CodeQL issues:

src/DemaConsulting.ReqStream/TraceMatrix.cs(245): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
src/DemaConsulting.ReqStream/TraceMatrix.cs(343): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variable to another variable](1) - consider mapping the sequence explicitly using '.Select(...)'.  
test/DemaConsulting.ReqStream.Tests/ContextTests.cs(656): 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.  

[Copilot]

@copilot I'm still seeing the following CodeQL issues:

src/DemaConsulting.ReqStream/TraceMatrix.cs(245): warning [cs/linq/missed-select] This foreach loop immediately [maps its iteration variabl...

Fixed all three remaining CodeQL issues in commit f31dca9:

1. TraceMatrix.cs:245 - Used .Select() and .Where() to map and filter child requirements
2. TraceMatrix.cs:343 - Used .Select() to map test names to results
3. ContextTests.cs:656 - Replaced try-finally with using statement for resource management

All tests pass and build completes with zero warnings.