Added 1.21.1 mod targets

- Build Fabric, Forge and NeoForge per target listed in gradle/mod-targets.json (1.21.1, 26.3)
- Add 1.21.1 adapter source overlays under adapters/*/src/versions/1.21.1
- Add verifyModdedMatrix and per-target Java runtime verification of loader jars
- Re-inject persistent dimensions from the levels-ready hook before the watchdog starts
- Wait for queued chunks and the final save before pregen completes
- Add the 1.21.1 data version and datapack supported_formats range
- Cascade regions whose sea or shore pool loses every biome
- Use Gson calls available on the 1.21.1 runtime

adapters/neoforge/src/versions/1.21.1/java/art/arcane/iris/neoforge/IrisNeoForgeBootstrap.java

@@ -0,0 +1,29 @@
+package art.arcane.iris.neoforge;
+
+import art.arcane.iris.modded.IrisModdedChunkGenerator;
+import art.arcane.iris.modded.ModdedEngineBootstrap;
+import art.arcane.iris.modded.ModdedLifecycleCallbacks;
+import art.arcane.iris.modded.service.ModdedTreeFellerService;
+import art.arcane.volmlib.nativelib.modded.NativeLoaderOptions;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeChunkGeneratorDefinition;
+import art.arcane.volmlib.nativelib.minecraft26_2.neoforge.NativeNeoForgeLoader;
+import art.arcane.volmlib.nativelib.minecraft26_2.neoforge.NativeNeoForgeBootstrap;
+import net.neoforged.bus.api.IEventBus;
+import net.neoforged.fml.common.Mod;
+import net.neoforged.fml.loading.FMLLoader;
+
+@Mod("irisworldgen")
+public final class IrisNeoForgeBootstrap {
+    public IrisNeoForgeBootstrap(IEventBus modBus) {
+        NativeNeoForgeLoader loader = new NativeNeoForgeLoader(new NativeLoaderOptions(
+                "irisworldgen", "treefeller", ModdedTreeFellerService::runBreakProbe));
+        NativeChunkGeneratorDefinition generator = IrisModdedChunkGenerator.DEFINITION;
+        ModdedEngineBootstrap.bootCommon(loader, "NeoForge " + FMLLoader.versionInfo().neoForgeVersion(),
+                () -> NativeNeoForgeBootstrap.registerGenerator(modBus, generator));
+        NeoForgeProtocolNetworking.register(modBus);
+        if (loader.clientEnvironment()) {
+            IrisNeoForgeClient.init(modBus);
+        }
+        NativeNeoForgeBootstrap.install(modBus, loader, ModdedLifecycleCallbacks.create());
+    }
+}

adapters/neoforge/src/versions/1.21.1/resources/META-INF/neoforge.mods.toml

@@ -0,0 +1,37 @@
+modLoader = "javafml"
+loaderVersion = "[3,)"
+license = "GPL-3.0"
+issueTrackerURL = "https://github.com/VolmitSoftware/Iris/issues"
+
+[[mixins]]
+config = "volmlib.entity.mixins.json"
+
+[[mixins]]
+config = "volmlib.client.mixins.json"
+
+[[accessTransformers]]
+file = "META-INF/accesstransformer.cfg"
+
+[[mods]]
+modId = "irisworldgen"
+version = "${version}"
+displayName = "Iris"
+description = "Iris World Generation Engine (NeoForge adapter - native chunk generator, explicit Iris world datapack workflow, engine lifecycle)"
+authors = "Arcane Arts (Volmit Software)"
+credits = "cyberpwn, NextdoorPsycho, Vatuu"
+displayURL = "https://docs.volmit.com/iris/"
+logoFile = "assets/irisworldgen/icon.png"
+
+[[dependencies.irisworldgen]]
+modId = "neoforge"
+type = "required"
+versionRange = "[21.1,21.2)"
+ordering = "NONE"
+side = "BOTH"
+
+[[dependencies.irisworldgen]]
+modId = "minecraft"
+type = "required"
+versionRange = "[${minecraftVersion}]"
+ordering = "NONE"
+side = "BOTH"