Refactoring improvements:
- Extract complex nested if-else logic into well-named private methods
- Separate concerns: each item type has its own update method
- Use constants for item names and quality limits
- Add comprehensive docstrings for all methods
- Improve code readability and maintainability
Conjured items implementation:
- Conjured items degrade in quality twice as fast as normal items
- After sell-by date, Conjured items degrade 4x faster (2x normal rate * 2x after sell-by)
- Quality never goes below 0
- Uses prefix matching for flexibility ('Conjured' prefix)
All tests pass, including the new Conjured items tests.
