Remove 7 empty test methods that contained only 'pass' statements:
- TestPipDetectionPlatformCompatibility (4 methods)
- TestPipDetectionRegression (3 methods)
Keep working tests that have actual logic and assertions.
- Convert virtual environment Python paths to absolute paths to ensure
consistency across different shell environments (Git Bash, WSL, etc.)
- Add enhanced diagnostic information when pip detection fails to help
users troubleshoot path and environment issues
- Improve error messages with specific guidance for different platforms
- Fix black configuration to exclude .zen_venv directory from formatting
- Add comprehensive test suite for pip detection edge cases
Fixes#188
