Create AGENTS.md with skill config

[JohnLudlow]

Create AGENTS.md with skill config

Project: GameEngineAdapter — Agent Configuration
Issue: N/A (infrastructure task)

PR Overview

This PR establishes portable agent configuration for the GameEngineAdapter repository by creating an AGENTS.md file with skill settings for the GitHub Copilot CLI harness. The configuration follows the jl-config pattern, enabling consistent behavior across planning, implementation, testing, and documentation workflows. Settings align with the project's C# library structure and existing docs/plans/ and docs/guides/ directories.

PR Detail

Files created:

• AGENTS.md — GitHub Copilot CLI harness configuration

Configuration added:

Planning & Feature Development:

• jl_planner and jl_feature_planner.plan_destination: github_issue, file_storage_location: docs/plans/
• Aligns plans with GitHub Issues for tracking and docs/plans directory for storage

Implementation:

• jl_tdd_implementer: implementation_style: red-green-refactor (enforces test-first for library code)
• jl_feature_implementer: code_style: csharp (C# style conventions)

Testing & Quality:

• jl_feature_tester and jl_tester: est_framework: xunit (standard for .NET)

Documentation:

• jl_feature_documenter and jl_documenter: doc_location: docs/guides/ (contributor documentation)

Prototyping:

• jl_prototype: plan_destination: inline_message (throwaway work stays in chat)

Mechanism:
Configuration follows jl-config precedence: AGENTS.md > CONTRIBUTING.md > agent defaults. Repository-relative paths ensure portability. Agents resolve settings gracefully with missing-file tolerance.

PR Impact

Breaking changes: None. This is a new infrastructure file.

User impact:

• Agents (jl_planner, jl_implementer, etc.) now inherit consistent harness configuration
• Plans automatically route to GitHub Issues and docs/plans/ directory
• TDD style enforced for implementation; test framework pre-configured to XUnit
• Improves consistency across planning and implementation workflows

Configuration override: Team-wide settings in CONTRIBUTING.md still take precedence over agent defaults (if CONTRIBUTING.md is updated later). Individual contributors can create local overrides if needed.

Backward compatibility: No breaking changes to existing code or APIs.

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Minor version bump recommended: repository infrastructure enhancement (infrastructure/configuration, no code change).