Build 1.21.6 with Stonecutter from the shared src/

1.21.6's copy only differed from 1.21.7's in RenderScopeImpl: item
rendering uses ItemRenderState, which 1.21.7 renamed to
KeyedItemRenderState. That's behind a version comment; 1.21.6 keeps its
older loader_version (0.18.5) in its gradle.properties.

Moving a version over leaves the old mc-<v> project's compiled classes in
the shared build/ folder, so a removed class (1.21.6's dead NameTagMixin)
still got packaged until a clean. VERSION_GUIDE now says to run
:<v>:clean once after moving a version.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/main/java/org/saturnclient/impl/ui/RenderScopeImpl.java

@@ -33,7 +33,10 @@ import net.minecraft.client.gui.render.state.TextGuiElementRenderState;
 import net.minecraft.client.gui.render.state.TexturedQuadGuiElementRenderState;
 import net.minecraft.client.gui.render.state.special.EntityGuiElementRenderState;
 import net.minecraft.client.render.entity.state.EntityRenderState;
+//? if >=1.21.7 {
 import net.minecraft.client.render.item.KeyedItemRenderState;
+//?} else
+//import net.minecraft.client.render.item.ItemRenderState;
 //? if >=1.21.11
 import net.minecraft.client.texture.AbstractTexture;
 import net.minecraft.client.texture.Sprite;
@@ -288,7 +291,10 @@ public class RenderScopeImpl implements RenderScope {
     private void drawItem(@Nullable LivingEntity entity, @Nullable World world, ItemStack stack, int x, int y, int seed,
             int z) {
         if (!stack.isEmpty()) {
+            //? if >=1.21.7 {
             KeyedItemRenderState keyedItemRenderState = new KeyedItemRenderState();
+            //?} else
+            //ItemRenderState keyedItemRenderState = new ItemRenderState();
             SaturnClient.client.getItemModelManager().clearAndUpdate(keyedItemRenderState, stack,
                     ItemDisplayContext.GUI, world,
                     entity, seed);