Add comprehensive GitHub Copilot instructions for git2jamf development

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed instructions for working effectively in the git2jamf codebase.

What's Included

The instructions cover all essential development workflows:

• Setup and Bootstrap: Exact commands for Python dependency installation (validated to take ~5 seconds)
• Build and Test: Complete linting workflow using flake8 with proper timeout expectations (<1 second)
• Repository Structure: Detailed breakdown of all key files and their purposes
• Development Workflow: Step-by-step process for making changes safely
• Validation Procedures: How to test changes without requiring Jamf Pro credentials

Key Features

• Validated Commands: Every command has been tested and timed to ensure accuracy
• Docker Build Warnings: Documents that Docker builds may fail in sandboxed environments due to network connectivity issues
• Environment Variable Reference: Complete list of expected inputs for understanding the action's behavior
• Troubleshooting Guide: Common issues and their solutions

Validation Results

All instructions have been thoroughly validated:

• ✅ Python dependencies install correctly (pip3 install -r requirements.txt)
• ✅ Linting works as expected (python3 -m flake8)
• ✅ Action script executes and fails gracefully without credentials
• ✅ Repository structure documentation is accurate
• ❌ Docker build documented to fail in constrained environments (expected behavior)

The instructions follow an imperative tone and provide specific timeout recommendations to prevent premature cancellation of long-running operations.

Fixes #12.

[!WARNING]

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• test.jamfcloud.com
  • Triggering command: python3 action.py (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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