Create comprehensive GitHub Copilot instructions for TZU development workflow

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file that provides validated, step-by-step instructions for working with the TZU codebase. The instructions were created through exhaustive testing and validation of all commands and workflows.

Key Features

Validated Build and Test Procedures

• Python API tests: 34 tests pass in ~15 seconds
• Frontend tests: 79 tests pass in ~10 seconds
• Dependency installation timing: Python (~45s), Node.js (~62s)
• All commands tested with appropriate timeout recommendations

Working Development Setup

• Standalone API development with SQLite and uvicorn
• React development server configuration with proper environment variables
• Manual validation scenarios for testing changes
• Health check endpoints and accessibility verification

Critical Issue Documentation

• Docker deployment fails due to SSL certificate issues with PyPI downloads
• Frontend build fails in CI due to ESLint treating warnings as errors (includes CI=false workaround)
• 490+ code quality issues documented as known/expected (don't prevent functionality)

Architecture Overview

• Backend: FastAPI with PostgreSQL, 34 passing tests
• Frontend: React with comprehensive test suite, 79 passing tests
• Key file locations and entry points clearly documented
• Configuration file guidance and environment setup

Manual Validation Workflows
The instructions include specific scenarios to test after making changes:

• API health check verification
• Swagger UI accessibility
• Frontend loading and authentication flows
• Risk assessment workflow validation

Timeout and Performance Guidance

• Explicit "NEVER CANCEL" warnings for long-running operations
• Measured timing data for all operations (builds, tests, installations)
• Recommended timeout values: 30+ minutes for tests, 60+ minutes for builds

The instructions prioritize working solutions over broken features, providing developers with reliable workflows while clearly documenting known limitations and workarounds.

Fixes #25.

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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.