Fix environment-dependent CI detection test

[milliondreams]

Problem

The CI detection test in crates/mandrel-mcp-th/src/cli/mod.rs is currently ignored because it fails in local environments where GitHub Actions environment variables are not set.

Details

• Test: test_ci_system_detection
• Issue: The test sets environment variables but the detection logic may not be working correctly
• Current Status: Temporarily ignored with #[ignore] attribute

Expected Behavior

The test should:

1. Properly set GitHub Actions environment variables
2. Detect the CI system correctly
3. Pass consistently across different environments

Suggested Fix

1. Review the CI detection logic in the EnvironmentDetector
2. Ensure environment variable setup in the test is complete
3. Add proper cleanup of environment variables
4. Consider using mock environments for testing

Priority

Medium - This is a test infrastructure issue that affects CI/CD validation.