Refine terrain and pregeneration

- Add coherent river width variation and shape source and terminal pools.
- Preserve separated hydrology intervals when checking river connectivity.
- Reduce footprint sorting, engine context lookup, and terrain blending work.
- Reuse modded snapshot validation after content and registry checks.
- Explain production pack update staging and restart requirements.
- Retain pregeneration map updates before its desktop window opens.
- Improve pregeneration layout, coordinate hover, keyboard controls, and error details.
- Add the new desktop labels to every supported language catalog.
- Add the buildPsychoLT entry point for verified platform outputs.
- Cover terrain, validation, and desktop behavior with regression tests.

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

@@ -6,10 +6,9 @@ import art.arcane.volmlib.nativelib.terrain.NativeWorld;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.configuration.IrisSettings;
 import art.arcane.iris.pack.BrokenPackException;
-import art.arcane.iris.pack.PackValidationCache;
+import art.arcane.iris.pack.PackFingerprints;
 import art.arcane.iris.pack.PackValidationRegistry;
 import art.arcane.iris.pack.PackValidationResult;
-import art.arcane.iris.pack.PackValidator;
 import art.arcane.iris.world.history.GenerationEpoch;
 import art.arcane.iris.world.history.GenerationEpochContractFactory;
 import art.arcane.iris.world.history.GenerationHistory;
@@ -174,7 +173,7 @@ final class ModdedGenerationHistoryStorage {
     static ActivePack resolveActive(GenerationHistory history) throws IOException {
         GenerationEpoch epoch = history.activeEpoch();
         Path packRoot = normalize(history.activePackRoot());
-        validatePack(packRoot, epoch.packFingerprint());
+        validatePack(packRoot);
         validateDimension(packRoot, epoch);
         return new ActivePack(
                 packRoot,
@@ -184,13 +183,16 @@ final class ModdedGenerationHistoryStorage {
         );
     }
 
-    private static void validatePack(Path packRoot, String fingerprint) {
-        String contextFingerprint = PackValidationCache.contextFingerprint();
-        PackValidationResult validation = PackValidator.validate(packRoot.toFile());
-        PackValidationRegistry.publish(packRoot, validation, fingerprint, contextFingerprint);
+    static PackValidationResult validatePack(Path packRoot) {
+        PackValidationResult validation = PackValidationRegistry.getMatching(
+                packRoot, PackFingerprints.computePackTreeFingerprint(packRoot.toFile()));
+        if (validation == null) {
+            validation = ModdedStartup.validatePack(packRoot.toFile());
+        }
         if (!validation.isLoadable()) {
             throw new BrokenPackException(packRoot.toString(), validation.getBlockingErrors());
         }
+        return validation;
     }
 
     private static void validateDimension(

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

@@ -119,7 +119,8 @@ public final class ModdedPackUpdateService implements ModdedTickableService {
                         + ", latest built-in release v" + update.version() + ".");
                 updates.add("Back up and review custom edits in " + new File(packsFolder, pack.name())
                         + "; close Studio, then update with /iris download pack=" + pack.name() + " overwrite=true.");
-                updates.add("Existing worlds retain their recorded production pack; this updates the authoring pack for new worlds.");
+                updates.add("Existing worlds retain their recorded production pack. Back up the complete world, then stage an update with /iris world update <dimension> "
+                        + pack.name() + " and restart the server to activate it.");
             }
         }
         notices = List.copyOf(updates);

adapters/modded-common/src/test/java/art/arcane/iris/modded/ModdedPackValidationPublicationTest.java

@@ -3,6 +3,7 @@ package art.arcane.iris.modded;
 import art.arcane.iris.modded.command.ModdedPackCommands;
 import art.arcane.iris.pack.BrokenPackException;
 import art.arcane.iris.pack.PackValidationRegistry;
+import art.arcane.iris.pack.PackValidationCache;
 import art.arcane.iris.pack.PackValidationResult;
 import art.arcane.iris.pack.PackValidator;
 import org.junit.After;
@@ -15,6 +16,7 @@ import java.io.File;
 import java.nio.file.Files;
 import java.nio.file.attribute.FileTime;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThrows;
@@ -22,6 +24,7 @@ import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
 
 public class ModdedPackValidationPublicationTest {
     @Rule
@@ -32,6 +35,55 @@ public class ModdedPackValidationPublicationTest {
         PackValidationRegistry.clear();
     }
 
+    @Test
+    public void repeatedSnapshotValidationParsesUnchangedPackOnce() throws Exception {
+        File root = temporaryFolder.newFolder("snapshot");
+        PackValidationResult result = loadable(root);
+        try (MockedStatic<PackValidator> validator = mockStatic(PackValidator.class)) {
+            validator.when(() -> PackValidator.validate(root)).thenReturn(result);
+            assertSame(result, ModdedGenerationHistoryStorage.validatePack(root.toPath()));
+            assertSame(result, ModdedGenerationHistoryStorage.validatePack(root.toPath()));
+            validator.verify(() -> PackValidator.validate(root), times(1));
+        }
+    }
+
+    @Test
+    public void snapshotValidationRejectsChangedBytesWithPreservedTimestamp() throws Exception {
+        File root = temporaryFolder.newFolder("snapshot");
+        File content = new File(root, "content.json");
+        Files.writeString(content.toPath(), "valid");
+        FileTime timestamp = Files.getLastModifiedTime(content.toPath());
+        PackValidationResult broken = new PackValidationResult(root.getName(), List.of("invalid"), List.of(), 1L);
+        try (MockedStatic<PackValidator> validator = mockStatic(PackValidator.class)) {
+            validator.when(() -> PackValidator.validate(root)).thenReturn(loadable(root), broken);
+            ModdedGenerationHistoryStorage.validatePack(root.toPath());
+            Files.writeString(content.toPath(), "wrong");
+            Files.setLastModifiedTime(content.toPath(), timestamp);
+            assertThrows(BrokenPackException.class,
+                    () -> ModdedGenerationHistoryStorage.validatePack(root.toPath()));
+            assertThrows(BrokenPackException.class,
+                    () -> ModdedGenerationHistoryStorage.validatePack(root.toPath()));
+            validator.verify(() -> PackValidator.validate(root), times(2));
+        }
+    }
+
+    @Test
+    public void snapshotValidationReparsesChangedRegistryContext() throws Exception {
+        File root = temporaryFolder.newFolder("snapshot");
+        AtomicReference<String> context = new AtomicReference<>("first");
+        PackValidationResult first = loadable(root);
+        PackValidationResult second = loadable(root);
+        try (MockedStatic<PackValidator> validator = mockStatic(PackValidator.class);
+             MockedStatic<PackValidationCache> cache = mockStatic(PackValidationCache.class)) {
+            cache.when(PackValidationCache::contextFingerprint).thenAnswer(ignored -> context.get());
+            validator.when(() -> PackValidator.validate(root)).thenReturn(first, second);
+            assertSame(first, ModdedGenerationHistoryStorage.validatePack(root.toPath()));
+            context.set("second");
+            assertSame(second, ModdedGenerationHistoryStorage.validatePack(root.toPath()));
+            validator.verify(() -> PackValidator.validate(root), times(2));
+        }
+    }
+
     @Test
     public void validationPublishesTheCanonicalRootAndPackName() throws Exception {
         File root = temporaryFolder.newFolder("terrain");

adapters/modded-common/src/test/java/art/arcane/iris/modded/service/ModdedPackUpdateServiceTest.java

@@ -65,6 +65,9 @@ public class ModdedPackUpdateServiceTest {
             verify(online, times(1)).sendMessage(contains("installed v1, latest built-in release v2"));
             verify(online, times(1)).sendMessage(contains(new File(root, "overworld").toString()));
             verify(online, times(1)).sendMessage(contains("/iris download pack=overworld overwrite=true"));
+            verify(online, times(1)).sendMessage(contains("Back up the complete world"));
+            verify(online, times(1)).sendMessage(contains("/iris world update <dimension> overworld"));
+            verify(online, times(1)).sendMessage(contains("restart the server to activate it"));
             verify(online, never()).sendMessage(contains("plugins/"));
             NativeProtocolPlayer later = player(true, false);
             service.notifyPlayer(later);