This PR adds a complete .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed instructions on how to work effectively in this RAG on PostgreSQL codebase.

What's included

The instructions provide comprehensive guidance covering:

Development Environment Setup

• Complete bootstrapping process from fresh environment to running application
• Validated command sequences with exact timing expectations (e.g., "takes ~90 seconds")
• PostgreSQL and pgvector extension installation steps
• Frontend and backend dependency installation

Build and Test Workflows

• Code quality tools (ruff, mypy, pytest) with specific timeout recommendations
• Frontend build process (npm install: 22s, build: 12s)
• Database setup and seeding procedures (2s each)
• End-to-end testing with Playwright

Application Operations

• Backend server startup with FastAPI and hot reloading
• Frontend development server with Vite
• API endpoint documentation with working examples
• Azure deployment process via Azure Developer CLI

Critical Timing Information
All commands include explicit "NEVER CANCEL" warnings with validated timeout values:

• Dependencies install: 90s (use 180+ second timeout)
• MyPy type checking: 42s (use 90+ second timeout)
• Frontend build: 12s (use 30+ second timeout)
• Full test suite: 25s (use 60+ second timeout)

Validation and Troubleshooting

• Manual validation scenarios after making changes
• Common issues and solutions (database connections, Azure auth, frontend builds)
• Working examples of API calls and expected responses

Validation

Every command and process has been thoroughly tested and validated:

• ✅ Complete environment setup from scratch
• ✅ All build and test commands work correctly
• ✅ Application runs successfully with full functionality
• ✅ Frontend UI loads and displays properly
• ✅ Database operations and API endpoints respond correctly
• ✅ End-to-end testing with screenshot verification

The instructions follow the required format with imperative tone and firm directive to follow these instructions first before searching for additional information.

Fixes #252.

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