Version content gate core

- Add the ContentGate, CompatWalker, PackCompatReport and finding types under core.compat
- Resolve block keys through the live registry, the legacy rename table, dimension blockFallbacks and the entry backup on every platform
- Move the legacy rename table into LegacyBlockRenames so Bukkit and the mod loaders apply it identically
- Evaluate every registrant on load from IrisData.preprocessObject and store the verdict on IrisRegistrant
- Add IrisDimension.blockFallbacks as a plain object property
- Keep missing palette keys as MissingBlockState placeholders so a chance-1 edit rule can still rewrite them
- Guard the modded rotator, merger and face fixer against non-modded states
- Source the legacy potion effect aliases from the gate so the Bukkit-typed table stays unloaded on modded

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

@@ -39,7 +39,9 @@ public final class ModdedDecoratorHooks implements DecoratorPlatformHooks.FaceFi
 
     @Override
     public PlatformBlockState fixFaces(PlatformBlockState state, Hunk<PlatformBlockState> hunk, int rX, int rZ, int x, int y, int z, EngineMantle mantle) {
-        ModdedBlockState fabric = (ModdedBlockState) state;
+        if (!(state instanceof ModdedBlockState fabric)) {
+            return state;
+        }
         BlockState cloned = fabric.handle();
         Map<String, BooleanProperty> allowed = faceProperties(cloned);
 

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

@@ -28,8 +28,9 @@ import java.util.Map;
 public final class ModdedStateMerger implements BlockDataMergeSupport.StateMerger {
     @Override
     public PlatformBlockState merge(PlatformBlockState base, PlatformBlockState update) {
-        ModdedBlockState fabricBase = (ModdedBlockState) base;
-        ModdedBlockState fabricUpdate = (ModdedBlockState) update;
+        if (!(base instanceof ModdedBlockState fabricBase) || !(update instanceof ModdedBlockState fabricUpdate)) {
+            return update;
+        }
         ModdedBlockState metadataSource = fabricUpdate.isCustom() ? fabricUpdate : fabricBase;
 
         try {

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

@@ -47,7 +47,9 @@ public final class ModdedStateRotator implements IrisObjectRotation.StateRotator
 
     @Override
     public PlatformBlockState rotate(IrisObjectRotation rotation, PlatformBlockState state, int spinxx, int spinyy, int spinzz) {
-        ModdedBlockState fabric = (ModdedBlockState) state;
+        if (!(state instanceof ModdedBlockState fabric)) {
+            return state;
+        }
         BlockState d = fabric.handle();
         boolean deleted = false;