Enchanter Letter

Since this update adds new logic, it is treated as a major version update.

1. The /letterstorage nbt command can now directly retrieve online players and bind to any entity using a UUID (when not in capture mode, it only retrieves NBT data; when in capture mode, it captures and binds to the target, allowing for item interactions);
2. All letters that can be upgraded through in-game actions can now be configured independently for items. Previously, the command only modified the configuration file when the player was unarmed; when holding the corresponding letter, it would modify only its NBT data;
3. New logic has been added for applying potion effects, using two different timing parameters to apply potion effects to players or mobs. Additional logic ensures these effects remain active and are not lost due to unloading or going offline. The command syntax is: /lettereffect add\delete\ls [ ...].