fix: execute Bukkit item use on the main thread

[twme-ai]

Summary

Run Bukkit item-use simulation on FAWE's synchronous task manager.

Problem

BukkitWorld.useItem() can be reached from FAWE's asynchronous execution
path. Paper's item-use implementation fires BlockCanBuildEvent, which must
run on the server thread, causing BlockCanBuildEvent may only be triggered synchronously.

The adapter call now follows the existing Bukkit integration convention and
uses TaskManager.taskManager().sync(...).

Testing

env JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 \
  ./gradlew -Dorg.gradle.configureondemand=false \
  :worldedit-bukkit:test --no-daemon

Also exercised on Paper 1.21.10 with a Mineflayer item-use brush: the expected
sapling was placed and Paper emitted no asynchronous Bukkit-event error.