deregisterFailedConstruction

De-registers a dungeon instance whose constructor body threw after super() had already registered it and started its scheduler tasks. Cancels every task and removes the instance from both registries so no orphaned WatchdogTask can keep it (and its world's ServerLevel) alive. The cloned world itself is deleted by the static cleanupLoadedWorld(world) call in the initializeInstancedWorld/initializeDynamicWorld catch block.