Apply template consistency updates from TemplateDotNetTool (Polyfill, LangVersion, ThrowIfNull, AgentFiles)

[Copilot]

Pull Request

Description

Syncs ReqStream with recent TemplateDotNetTool template changes (PRs #41, #43, #45, #46).

Source project (DemaConsulting.ReqStream.csproj)

• LangVersion: 12 → latest
• Added Polyfill 9.12.0 source-only package
• Updated SonarAnalyzer.CSharp: 10.19.0 → 10.20.0.135146
• Added structured comments to package reference groups (PrivateAssets rationale)

Test project (DemaConsulting.ReqStream.Tests.csproj)

• Added <Using Include="Polyfills" /> implicit using
• Updated Microsoft.NET.Test.Sdk: 18.0.1 → 18.3.0
• Updated SonarAnalyzer.CSharp: 10.19.0 → 10.20.0.135146

Code modernization (Context.cs, Validation.cs)

• Added ArgumentNullException.ThrowIfNull guards to Context.Create and Validation.Run

Agent configuration (AGENTS.md, .github/agents/*.md)

• Replaced verbose AGENTS.md with concise quick-reference format matching the template (removed sections that duplicated individual agent file content)
• Updated AGENTS.md: "C# 12" → "C# latest", TemplateTool_* → ReqStream_* test naming
• Added missing Test Source Filters section to .github/agents/requirements-agent.md
• Added missing Test Source Filters section to .github/agents/test-developer.md
• Added full MSTest V4 Best Practices section (5 antipatterns) to .github/agents/test-developer.md
• Added missing Tracking Template Evolution section to .github/agents/repo-consistency-agent.md
• Fixed markdownlint config filename (.markdownlint.json → .markdownlint-cli2.jsonc) in code-quality-agent.md and repo-consistency-agent.md

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.ReqStream --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

Boolean capitalization fix (template PR #44) was already applied in ReqStream — no change needed.

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[Malcolmnixon]

This file doesn't seem to follow the same pattern as the template. This has extra/unnecessary sections like replicating the assert/test best practices. Please use the repo-consistency agent to actually make this consistent. Don't just keep stuff around because "well it was there before" - I'm trying to make these projects have consistent agent configurations so the agents function essentially identically. Please do the same not just for this file, but for all the agent config files.

[Copilot]

Done in commit ca52cd9. AGENTS.md has been replaced with the concise quick-reference format matching the template (removed duplicated Testing Guidelines, Code Style, Pre-Finalization Checklists, etc.). The .github/agents/ files were also synced: added missing Test Source Filters sections to requirements-agent.md and test-developer.md, added missing Tracking Template Evolution section to repo-consistency-agent.md, and fixed the markdownlint filename reference in code-quality-agent.md and repo-consistency-agent.md.