Add GitHub agents from TemplateDotNetTool and update AGENTS.md

[Copilot]

Adopts the standardized agent definitions from TemplateDotNetTool into SpdxTool, adding the .github/agents/ directory and reformatting AGENTS.md as a quick-reference guide. Also migrates the markdownlint configuration from .markdownlint.json to .markdownlint-cli2.jsonc to align with the TemplateDotNetTool pattern.

Description

New .github/agents/ directory with 6 specialized agents adapted for SpdxTool:

• software-developer.md — production code, self-validation tests (SpdxTool_* naming)
• test-developer.md — unit/integration tests in test/DemaConsulting.SpdxTool.Tests/
• technical-writer.md — documentation with SpdxTool-specific markdown link style rules
• requirements-agent.md — requirements guidance without requirements.yaml enforcement
• code-quality-agent.md — linting/static analysis gates for SpdxTool toolchain
• repo-consistency-agent.md — special case: reviews SpdxTool for drift against the TemplateDotNetTool template

AGENTS.md reformatted to match TemplateDotNetTool's quick-reference structure: tech stack, key files, code style, build/test commands, and an "Available Specialized Agents" section linking to the new agent files.

Migrated from .markdownlint.json to .markdownlint-cli2.jsonc:

• Created .markdownlint-cli2.jsonc matching the TemplateDotNetTool format, with AGENT_REPORT_*.md exclusion built into the config's ignores field
• Removed the old .markdownlint.json
• Updated .github/workflows/build.yaml to reference .markdownlint-cli2.jsonc
• Updated AGENTS.md and agent files (code-quality-agent.md, repo-consistency-agent.md) to reference the new config filename

AGENT_REPORT_*.md exclusions wired up across:

• .gitignore — prevent accidental commits of inter-agent report files
• .cspell.json — skip spell-check on report files; also adds TemplateDotNetTool, markdownlint, yamllint, mstest to the word list
• .markdownlint-cli2.jsonc — AGENT_REPORT_*.md excluded via the ignores field

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 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

The repo-consistency-agent.md intentionally differs from the TemplateDotNetTool version: rather than reviewing downstream repos, it checks this repo (SpdxTool) against TemplateDotNetTool as the upstream template.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.