[WIP] ✨ Set up Copilot instructions

[Copilot]

• Analyzed repository structure and identified Jekyll-based website
• Successfully installed Ruby dependencies using Bundler
• Validated Jekyll build process (takes ~1 second)
• Tested Jekyll development server functionality
• Verified all main navigation pages load correctly (200 status)
• Tested individual member and publication pages work
• Create comprehensive .github/copilot-instructions.md file
• Include exact command timing and validation scenarios
• Add specific timeout warnings and build instructions
• Document manual validation requirements

Fixes #3.

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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.