Improve README documentation accuracy and completeness
- Fix field naming discrepancies (Menu parent → Parent menu link, Expanded → All menus entries expanded)
- Clarify Description field is only available after initial save
- Add menu existence as prerequisite
- Remove non-functional debug page reference
- Update depth configuration to reflect actual 1-9 range
- Enhance documentation structure with better organization
Addresses feedback from issue #3513980
Co-Authored-By: Claude noreply@anthropic.com
Closes #3513980