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/test/java/art/arcane/iris/modded/ModdedPlatformPathsTest.java

@@ -9,6 +9,9 @@ import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedServerAccess;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedServerLevels;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.EntitySpawnReason;
+import net.minecraft.world.entity.Mob;
+import net.minecraft.world.level.ServerLevelAccessor;
 import net.minecraft.world.level.block.state.BlockState;
 import org.junit.Rule;
 import org.junit.Test;
@@ -83,6 +86,11 @@ public class ModdedPlatformPathsTest {
             public boolean canBreakBlock(ServerLevel level, ServerPlayer player, BlockPos position, BlockState state) {
                 return false;
             }
+
+            @Override
+            public boolean checkSpawnPosition(Mob mob, ServerLevelAccessor level, EntitySpawnReason reason) {
+                return false;
+            }
         });
     }