Loader spawn position check

- The modded chunk generator hands VolmLib the bound loader for chunk-generation creature checks
- Each loader build tests its spawn position check: Forge and NeoForge fire MobSpawnEvent.PositionCheck and honor a denial, Fabric applies the vanilla rule and obstruction checks

adapters/modded-common/src/main/java/art/arcane/iris/modded/IrisModdedChunkGenerator.java

@@ -44,6 +44,7 @@ import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeFeatureBiomeSourc
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeDimensionRuntime;
 
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedLoader;
 
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeGeneratorOwner;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeGeneratorHandle;
@@ -1011,6 +1012,11 @@ public final class IrisModdedChunkGenerator implements NativeGeneratorOwner, Nat
         return ModdedEngineBootstrap.currentServer();
     }
 
+    @Override
+    public NativeModdedLoader loader() {
+        return ModdedEngineBootstrap.loader();
+    }
+
     @Override
     public Engine current() {
         return engine();