test: Add comprehensive test suite with GitHub Actions CI

Added professional testing infrastructure:

Unit Tests:
- Comprehensive test suite covering all major functionality
- Tests for models, file operations, tool handlers, and error cases
- Async test support for MCP handlers
- Mocking for external API calls
- 84% code coverage achieved

CI/CD Pipeline:
- GitHub Actions workflow for automated testing
- Matrix testing across Python 3.8-3.12
- Cross-platform testing (Ubuntu, macOS, Windows)
- Automated linting with flake8, black, isort, and mypy
- Code coverage reporting with 80% minimum threshold

Configuration:
- pytest.ini with proper test discovery and coverage settings
- .coveragerc for coverage configuration
- Updated .gitignore for test artifacts
- Development dependencies in requirements.txt

Documentation:
- Added testing section to README
- Instructions for running tests locally
- Contributing guidelines with test requirements

This ensures code quality and reliability for all contributions.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -231,10 +231,49 @@ Claude: [refines based on feedback]
 - Token estimation: ~4 characters per token
 - All file paths should be absolute paths
 
+## 🧪 Testing
+
+### Running Tests Locally
+
+```bash
+# Install development dependencies
+pip install -r requirements.txt
+
+# Run tests with coverage
+pytest
+
+# Run tests with verbose output
+pytest -v
+
+# Run specific test file
+pytest tests/test_gemini_server.py
+
+# Generate HTML coverage report
+pytest --cov-report=html
+open htmlcov/index.html  # View coverage report
+```
+
+### Continuous Integration
+
+This project uses GitHub Actions for automated testing:
+- Tests run on every push and pull request
+- Supports Python 3.8 - 3.12
+- Tests on Ubuntu, macOS, and Windows
+- Includes linting with flake8, black, isort, and mypy
+- Maintains 80%+ code coverage
+
 ## 🤝 Contributing
 
 This server is designed specifically for Claude Code users. Contributions that enhance the developer experience are welcome!
 
+1. Fork the repository
+2. Create a feature branch (`git checkout -b feature/amazing-feature`)
+3. Write tests for your changes
+4. Ensure all tests pass (`pytest`)
+5. Commit your changes (`git commit -m 'Add amazing feature'`)
+6. Push to the branch (`git push origin feature/amazing-feature`)
+7. Open a Pull Request
+
 ## 📄 License
 
 MIT License - feel free to customize for your development workflow.