Add --biomes flag for biome-only chunk import

src/main/java/net/querz/mcaselector/cli/ParamExecutor.java

@@ -129,6 +129,10 @@ public final class ParamExecutor {
 			.desc("One or a range of section indices to import into the target world during chunk import")
 			.hasArg()
 			.get());
+		options.addOption(Option.builder()
+			.longOpt("biomes")
+			.desc("Import only biome data, not blocks or entities")
+			.get());
 		options.addOption(Option.builder()
 			.longOpt("render-height")
 			.desc("The highest Y level to render in image mode")
@@ -685,6 +689,11 @@ private void saveSelection(Selection selection, File output) throws RuntimeExcep
 	}
 
 	private List<Range> parseSections(boolean mandatory) throws ParseException {
+		// If --biomes is set, return empty list (special flag for biomes-only import)
+		if (line.hasOption("biomes")) {
+			return new ArrayList<>();
+		}
+
 		if (!line.hasOption("sections")) {
 			if (mandatory) {
 				throw new ParseException("missing mandatory sections parameter");

src/main/java/net/querz/mcaselector/version/ChunkFilter.java

@@ -106,6 +106,42 @@ interface Merge {
 
 		CompoundTag newEmptyChunk(Point2i absoluteLocation, int dataVersion);
 
+		// Biomes-only merge for modern Minecraft (1.18+)
+		default void mergeBiomesOnly(CompoundTag source, CompoundTag destination) {
+			// In Minecraft 1.18+, biomes are stored in sections
+			if (source.containsKey("sections") && destination.containsKey("sections")) {
+				ListTag sourceSections = source.getListTag("sections");
+				ListTag destSections = destination.getListTag("sections");
+
+				if (sourceSections != null && destSections != null) {
+					// Create map of Y -> Section for fast lookup
+					java.util.Map<Integer, CompoundTag> destSectionMap = new java.util.HashMap<>();
+					for (Tag tag : destSections) {
+						if (tag instanceof CompoundTag section) {
+							int y = section.getInt("Y");
+							destSectionMap.put(y, section);
+						}
+					}
+
+					// Copy biomes from source sections
+					for (Tag tag : sourceSections) {
+						if (tag instanceof CompoundTag sourceSection) {
+							int y = sourceSection.getInt("Y");
+							CompoundTag destSection = destSectionMap.get(y);
+
+							if (destSection != null && sourceSection.containsKey("biomes")) {
+								// Copy biome palette
+								Tag biomeData = sourceSection.get("biomes");
+								if (biomeData != null) {
+									destSection.put("biomes", biomeData.copy());
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+
 		default ListTag mergeLists(ListTag source, ListTag destination, List<Range> ranges, Function<Tag, Integer> ySupplier, int yOffset) {
 			ListTag result = new ListTag();
 			for (Tag dest : destination) {

src/main/java/net/querz/mcaselector/version/java_1_18/ChunkFilter_21w43a.java

@@ -633,6 +633,12 @@ public static class Merge extends ChunkFilter_21w06a.Merge {
 
 		@Override
 		public void mergeChunks(CompoundTag source, CompoundTag destination, List<Range> ranges, int yOffset) {
+			// Empty ranges list = biomes-only mode
+			if (ranges != null && ranges.isEmpty()) {
+				mergeBiomesOnly(source, destination);
+				return;
+			}
+
 			mergeCompoundTagLists(source, destination, ranges, yOffset, "sections", c -> ((CompoundTag) c).getInt("Y"));
 			mergeCompoundTagLists(source, destination, ranges, yOffset, "block_entities", c -> ((CompoundTag) c).getInt("y") >> 4);
 			mergeCompoundTagLists(source, destination, ranges, yOffset, "block_ticks", c -> ((CompoundTag) c).getInt("y") >> 4);