Add comprehensive GitHub Copilot instructions for Roberts Lab resources repository

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed guidance for working effectively in the Roberts Lab resources repository.

What this adds

The instruction file provides imperative, actionable guidance covering:

Build System & Validation

• MkDocs with Material theme build process (~1 second build time)
• Development server setup and testing procedures
• Explicit timeout values (30+ seconds for builds, 300+ seconds for deployments)
• "NEVER CANCEL" warnings for all time-consuming operations

Repository Structure & Navigation

• Complete directory layout (docs/, protocols/, equipment_manuals/)
• Configuration files (mkdocs.yml, docs/requirements.txt, .readthedocs.yml)
• GitHub Actions workflows for auto-deployment and URL checking

Validation Requirements

• Mandatory manual testing scenarios (homepage, computing guides, protocols)
• Pre-commit validation steps (mkdocs build + development server testing)
• Expected build warnings and success indicators
• Quality assurance guidelines for content changes

Troubleshooting & Common Issues

• Network timeout handling for pip installations
• Theme fallback options (readthedocs theme when material theme unavailable)
• Common build warnings that are expected and normal
• Performance expectations and timing guidelines

Validation completed

All documented commands have been thoroughly tested:

• ✅ Build process timing measured (~1 second consistently)
• ✅ Development server functionality verified
• ✅ Manual validation scenarios tested (homepage, computing guides, protocols accessible)
• ✅ Dependency installation process documented with fallback options
• ✅ GitHub Actions workflow commands validated

The instructions follow the imperative tone requirement ("Run this command", "Do not do this") and provide exhaustive detail to ensure any developer can follow the instructions and have them work reliably.

Fixes #2275.

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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.