Add comprehensive GitHub Copilot instructions for OOW development workflow

[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 OOW codebase.

What's Included

The instructions provide a complete development guide covering:

• Essential commands with validated timing information (all operations complete in under 10 seconds)
• Project structure overview showing key directories and files
• Complete validation workflow that must be followed before committing changes
• Manual testing procedures to verify library functionality works correctly
• CI/CD requirements and quality gates that must be met
• Development patterns for adding new extensions and objects

Validation Process

Every command and procedure in the instructions has been exhaustively validated to ensure they work correctly:

# All commands are fast and reliable
npm install     # ~0.5 seconds
npm run lint    # ~1.9 seconds  
npm test        # ~0.6 seconds (120 tests)
npm run coverage # ~2.2 seconds (100% coverage)

The instructions include specific timeout recommendations and "NEVER CANCEL" warnings to prevent premature command termination, along with complete functionality testing scenarios to verify the OOW extensions work correctly.

Key Features

• Imperative tone with clear "Run this command" directives
• Exhaustive validation - every instruction has been tested to work correctly
• Time expectations - explicit timing for all operations to set proper expectations
• Manual testing scenarios - specific validation steps to verify functionality
• Comprehensive coverage - answers all common questions developers would have

The instructions start with a firm directive to always follow the provided guidance first, only falling back to additional search when information is incomplete or incorrect.

Fixes #72.

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