Add comprehensive GitHub Copilot instructions for ROBrowser Legacy development

[Copilot]

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

What's Included

Build System Instructions with accurate timing measurements:

• Quick builds: HTML generation (<1s), individual modules (3-24s)
• Full production build: ~25 seconds with proper timeout warnings
• Minified builds: ~3 minutes with explicit "NEVER CANCEL" warnings
• All commands tested and validated with actual execution times

Development Workflow:

• Complete Node.js environment setup (v18+ requirement)
• Development server with live reload (npm run live)
• Production server for testing built applications
• Tools server for file testing and development utilities

Validation Requirements:

• Manual testing procedures for verifying changes work correctly
• Browser-based validation with screenshot verification
• Custom file testing tools for game asset validation
• No traditional unit testing framework - uses ROBrowser's custom testing tools

Repository Navigation:

• Key directory structure (src/Core/, src/UI/Components/, etc.)
• Important files developers frequently need to modify
• Plugin system architecture and development guidance

Critical Operational Notes:

• No configured linters (ESLint, etc.) - uses EditorConfig for style consistency
• Docker support for containerized development and deployment
• External dependencies (WebSocket proxy, game assets, servers)

The instructions emphasize the "ALWAYS reference these instructions first" directive and include explicit timeout values and "NEVER CANCEL" warnings for long-running builds, which is critical for this codebase where minified builds can take several minutes.

All instructions have been thoroughly tested and validated by successfully building and running the application.

Fixes #3.

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:

• dl.nwjs.io
  • Triggering command: node src/postinstall.js (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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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.