New Commands:
- z read - Smart file reader with auto-detection (markdown, syntax highlighting)
- z sys - System overview (CPU, RAM, Disk, processes)
- z find - File search with pattern/size/time filters
- z search - User-friendly grep alternative
- z usage - Process resource usage monitor
Enhancements:
- Unified help system with consistent error messages
- Help on error shows usage and examples for each command
- "Command not found" suggests similar commands
- Directory info now detects .gitignore and shows ignored files
- File handler registry for extensible file type detection
- Added Italic, Dim, Underline color constants
