Enhance CI/CD pipeline and add comprehensive integration tests

[SL-Mar]

Summary

This PR significantly improves the project's CI/CD infrastructure and testing coverage by enhancing the GitHub Actions workflow, adding comprehensive integration tests, and creating contributor documentation.

Key Changes

CI/CD Pipeline Improvements

• Enhanced test reporting: Added --cov-report=term and --cov-fail-under=50 to pytest to enforce minimum coverage threshold and display coverage in terminal
• Upgraded codecov action: Updated from v3 to v4 with explicit token configuration for more reliable coverage reporting
• Stricter coverage enforcement: Changed fail_ci_if_error from false to true to fail builds when coverage upload fails
• Improved security scanning: Modified pip-audit to install dev dependencies and use --strict flag for stricter vulnerability checking
• New integration test job: Added dedicated integration job that runs after lint and type-check, with proper dependencies and markers for selective test execution

Comprehensive Integration Tests

• New test file: tests/test_integration.py with 561 lines of integration tests covering:
  • CLI smoke tests for all major commands (search, download, summarize, generate, validate, backtest, auto, library, evolve, config-show)
  • Search command integration tests with mocked APIs
  • Generate command tests with mocked LLM responses
  • Validate command tests for both valid and invalid code
  • Autonomous mode (auto) command tests
  • Library builder command tests
  • Evolution (evolve) command tests
  • End-to-end workflow tests combining multiple commands
  • Error handling tests for missing API keys, network errors, and invalid inputs
• Proper test organization: Uses pytest markers (@pytest.mark.integration) for selective test execution
• Comprehensive mocking: All external service calls are properly mocked to ensure tests are isolated and fast

Documentation

• New CONTRIBUTING.md: Comprehensive contributor guide including:
  • Code of conduct reference
  • Development setup instructions with virtual environment setup
  • Testing guidelines with examples
  • Code quality tools and commands
  • Branch naming conventions and commit message format
  • Pull request process and review guidelines
  • Coding standards and security best practices
  • Documentation requirements
  • Test organization and markers

Implementation Details

• Integration tests use Click's CliRunner for testing CLI commands without actual execution
• All external dependencies (APIs, LLMs, file systems) are mocked using unittest.mock
• Tests are organized into logical test classes for better maintainability
• Fixtures provide reusable test setup (CLI runner, mock environment)
• Error handling tests verify graceful degradation and helpful error messages
• End-to-end workflow tests demonstrate realistic usage patterns

Benefits

• Improved code quality: Enforced minimum coverage threshold prevents regression
• Better reliability: Integration tests catch CLI-level issues before production
• Easier onboarding: CONTRIBUTING.md provides clear guidelines for new contributors
• Stronger security: Stricter pip-audit checks catch more vulnerabilities
• Better visibility: Terminal coverage reports provide immediate feedback to developers