Fixed wandering trader spawning

- World injection attaches vanilla event spawners for NORMAL dimension environments
- Covers worlds loaded at server start, Studio worlds and Folia worlds
- Binding test covers overworld and nether environments

core/src/main/java/art/arcane/iris/platform/bukkit/nms/BukkitBinding.java

@@ -9,6 +9,7 @@ import art.arcane.iris.spi.PlatformGenerationRegistry;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.structure.nativegen.IrisImportedStructureControl;
 import art.arcane.iris.structure.nativegen.NativeStructureVolumeIndex;
+import art.arcane.iris.world.IrisEnvironment;
 import art.arcane.iris.world.history.SavedTerrainChunk;
 import art.arcane.volmlib.nativelib.NativeAdapters;
 import art.arcane.volmlib.nativelib.terrain.NativeTerrainAccess;
@@ -104,6 +105,9 @@ public final class BukkitBinding implements INMSBinding {
     public void inject(long seed, Engine engine, World world) throws NoSuchFieldException, IllegalAccessException {
         validateDimension(engine, world, generation.dimension(world));
         generation.inject(world, new BukkitGeneratorContext(new BukkitGeneratorContext.Options(seed, engine, world)));
+        if (engine.getDimension().getEnvironment() == IrisEnvironment.NORMAL) {
+            generation.attachOverworldSpawners(world);
+        }
     }
 
     @Override

core/src/test/java/art/arcane/iris/platform/bukkit/nms/BukkitBindingTest.java

@@ -1,5 +1,9 @@
 package art.arcane.iris.platform.bukkit.nms;
 
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import art.arcane.iris.generation.terrain.IrisDimensionRuntimeContract;
+import art.arcane.iris.world.IrisEnvironment;
 import art.arcane.volmlib.nativelib.terrain.NativeGenerationRegistry;
 import art.arcane.volmlib.nativelib.terrain.NativeTerrainAccess;
 import art.arcane.volmlib.nativelib.terrain.NativeTerrainSnapshots;
@@ -7,8 +11,12 @@ import art.arcane.volmlib.nativelib.terrain.NativeWorldGeneration;
 import art.arcane.volmlib.nativelib.terrain.NativeWorldLifecycleFactory;
 import org.bukkit.World;
 import org.junit.Test;
+
+import java.util.Locale;
+
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -37,13 +45,38 @@ public class BukkitBindingTest {
         verify(fixture.lifecycle).releasePluginClassLoaderClose();
     }
 
+    @Test
+    public void injectAttachesVanillaSpawnersOnlyToOverworldEnvironments() throws NoSuchFieldException, IllegalAccessException {
+        Fixture fixture = new Fixture();
+        World overworld = injectedWorld(fixture, IrisEnvironment.NORMAL);
+        World nether = injectedWorld(fixture, IrisEnvironment.NETHER);
+        verify(fixture.generation).attachOverworldSpawners(overworld);
+        verify(fixture.generation, never()).attachOverworldSpawners(nether);
+    }
+
+    private static World injectedWorld(Fixture fixture, IrisEnvironment environment) throws NoSuchFieldException, IllegalAccessException {
+        IrisDimension dimension = new IrisDimension();
+        dimension.setLoadKey(environment.name().toLowerCase(Locale.ROOT));
+        dimension.setEnvironment(environment);
+        IrisDimensionRuntimeContract contract = IrisDimensionRuntimeContract.expected(dimension, "iris");
+        Engine engine = mock(Engine.class);
+        when(engine.getDimension()).thenReturn(dimension);
+        World world = mock(World.class);
+        when(world.getMinHeight()).thenReturn(contract.minHeight());
+        when(world.getMaxHeight()).thenReturn(contract.minHeight() + contract.height());
+        when(fixture.generation.dimension(world)).thenReturn(new NativeWorldGeneration.Dimension(contract.typeKey(),
+                contract.minHeight(), contract.height(), contract.logicalHeight(), contract.minHeight(), contract.height()));
+        fixture.binding.inject(1L, engine, world);
+        return world;
+    }
+
     private static final class Fixture {
         private final NativeTerrainAccess terrain = mock(NativeTerrainAccess.class);
+        private final NativeWorldGeneration generation = mock(NativeWorldGeneration.class);
         private final NativeWorldLifecycleFactory.Controller lifecycle = mock(NativeWorldLifecycleFactory.Controller.class);
         private final BukkitBinding binding;
 
         private Fixture() {
-            NativeWorldGeneration generation = mock(NativeWorldGeneration.class);
             when(generation.lifecycle(BukkitWorldLifecyclePolicy.INSTANCE)).thenReturn(lifecycle);
             binding = new BukkitBinding(new BukkitBinding.Capabilities(terrain, generation,
                     mock(NativeTerrainSnapshots.class), mock(NativeGenerationRegistry.class)));