NeoForge 1.21.1 port

[F0x06]

Ports ChemLib from Forge 1.20.1 to NeoForge 1.21.1 (Java 21). No gameplay, recipe, or content changes — same elements, same compounds, same behavior.

[Dark-Arcana]

Items to address before merge:

1. RecipeGenerator.buildRecipes is empty. The method body was deleted. Recipes still load at runtime because the previously-generated JSONs were renamed (from recipes/ to recipe/) and updated ("item" to "id") directly under src/generated/resources/. However, ./gradlew runData no longer regenerates them. Any future change to recipe shape requires editing approximately 385 JSON files manually. Restore the recipe generation code. The 1.21 API is buildRecipes(RecipeOutput), used with ShapedRecipeBuilder.shaped(RecipeCategory.MISC, ...).save(output, ResourceLocation.fromNamespaceAndPath(...)).

2. Config.loadConfig is dead code. NeoForge 1.21's ModContainer.registerConfig(ModConfig.Type, IConfigSpec) handles config file creation, loading, and reload events automatically. The previous manual loading code is no longer required, and the empty method body confirms this. Delete the empty loadConfig method and remove the Config.loadConfig(...) call from the ChemLib constructor.

3. Attribute-modifier tooltips removed from FluidEffectsTooltipUtility.addTooltipEffects. The old code iterated over MobEffect.getAttributeModifiers() and added lines such as "+5 Max Health" to chemical-fluid bucket tooltips. The new code removes this section. The 1.21 replacement API is MobEffectInstance.forEachModifier(EquipmentSlotGroup, BiConsumer). Port the modifier-tooltip logic to the new API. The current code is a behavior regression.

4. Mod-namespace tooltip line removed from chemical, element, and compound item tooltips and from bucket tooltips. The old appendHoverText overloads in ChemicalItem, CompoundItem, ElementItem, and ForgeEventHandler.gatherTooltipComponents added a styled "Chemlib" line at the bottom of tooltips using MOD_ID_TEXT_STYLE. All four locations were removed. NeoForge 1.21 does not automatically add a mod-source line to item tooltips. JEI and REI add it themselves, but vanilla and NeoForge do not. Restore the line in all four locations.

5. ForgeEventHandler class name is misleading after the port. The class now subscribes to EventBusSubscriber.Bus.GAME and no longer uses the Forge event bus. Rename the class to GameEventHandler.

6. Release notes for downstream consumers (Alchemistry):

   • Element.getGroupName() becomes getGroupKey(). The return value is a translation key, not a literal display string. Consumers must pass the value through Component.translatable(...).
   • BlockTagGenerator and ItemTagGenerator migrate tags from the forge: namespace to c:. This follows NeoForge 1.21's adoption of the cross-loader Common namespace (also used by Fabric). Any datapack that references #forge:dusts/iron, #forge:storage_blocks/iron, and similar tags must update its references to #c:....
   • ChemicalLiquidBlock constructor signature changes from Supplier<? extends FlowingFluid> to FlowingFluid.