what it does:
- /staff <username> opens a GUI (owner-only, checked against a username list in config.yml, not OP/permissions)
- Click any of the 8 rank icons to set that rank directly, or use the Promote/Demote arrows to move one step up/down your ladder: Builder → Helper → JR Mod → Mod → Manager → JR Admin → Admin → Developer
- /staff reload reloads the owner list and rank ladder from config without a restart
- Rank names, LuckPerms group names, and GUI icons are all editable in config.yml — no recompiling needed for those changes
