Add GitHub Copilot agents and skills for chef-cli

[sanghinitin]

Summary

Add GitHub Copilot custom agents and skills for the chef-cli repository to improve AI-assisted development workflows.

Changes

Agents Added

• chef-command-expert — Expert in Chef CLI command architecture and implementation patterns
• habitat-agent — Specialist for Habitat package plans, build failures, and Studio issues (includes .agent.md for VS Code integration)
• ruby-agent — Ruby code reviewer for cookstyle compliance, idioms, security, and performance
• testing-agent — RSpec test generator ensuring >80% coverage and repository test patterns

Skills Added

• debug-chef-cli — Step-by-step skill for debugging CLI command errors, policyfile issues, and test failures
• develop-loop — Iterative develop-build-test-fix cycle for feature development and bug fixes
• update-cli-command — Guide for adding or modifying built-in CLI commands
• write-rspec-tests — RSpec unit test writing following repository conventions
• habitat-packaging — Habitat package creation, validation, and maintenance

Supporting Files

• .github/prompt.md — Shared prompt instructions
• .github/cli-architecture.md — CLI architecture reference for agents

Testing

No functional code changes — these are GitHub Copilot configuration files only (.github/agents/, .github/skills/).

Labels

• Aspect: Documentation
• Expeditor: Skip All

[github-actions]

Simplecov Report

Covered	Threshold
98.51%	90%