Add BetterMace Fabric mod for Minecraft 1.21.4

[devin-ai-integration]

Summary

Adds a self-contained Fabric mod under minecraft-mods/bettermace/ that improves the vanilla Mace weapon in Minecraft 1.21.4. This is a new top-level subdirectory in the repo and does not touch any existing DeepSeek-Math code.

What the mod does (all toggleable / tuneable via config/bettermace.json):

• AOE smash attack — when a real smash hit lands (fall distance > threshold, not elytra-flying), nearby LivingEntitys around the primary target also take a fraction of the fall-distance bonus damage and get knocked outward. Radius scales with fall distance up to a cap.
• Optional lightning bolt on extreme falls (off by default; cosmetic-only by default when enabled).
• Optional self-bounce for the attacker after a smash (extra vertical impulse on top of Wind Burst).
• Skips spectators and (optionally) teammates.
• Plays MACE_SMASH_GROUND_HEAVY + SWEEP_ATTACK particles for the AOE.

Implementation: a single mixin (MaceItemMixin) @Injects at HEAD of net.minecraft.item.MaceItem#postHurtEnemy. Config is a simple GSON-serialized POJO in FabricLoader.getConfigDir()/bettermace.json, auto-created on first load.

Files added (all new, under minecraft-mods/bettermace/):

• build.gradle, settings.gradle, gradle.properties, gradle/wrapper/gradle-wrapper.properties, .gitignore
• src/main/resources/fabric.mod.json, bettermace.mixins.json
• src/main/java/dev/bettermace/BetterMace.java (entrypoint)
• src/main/java/dev/bettermace/config/BetterMaceConfig.java
• src/main/java/dev/bettermace/mixin/MaceItemMixin.java
• README.md (RU)

Review & Testing Checklist for Human

This PR was not built or run locally — there is no JDK 21 / fabric-loom toolchain in the session, and the Minecraft/Yarn/Fabric-API artifacts were not fetched. Treat every interaction with Minecraft internals below as unverified.

• Run ./gradlew build locally with JDK 21. Note: only gradle-wrapper.properties was committed — gradle-wrapper.jar, gradlew, and gradlew.bat are not in the repo, so you'll need to run gradle wrapper once (with a system Gradle 8.10.2) to generate them before ./gradlew build will work. Consider whether you want those wrapper files committed.
• Verify Yarn method name postHurtEnemy actually exists on net.minecraft.item.MaceItem at yarn 1.21.4+build.8. The method was renamed from postHit somewhere in the 1.21.x line; if 1.21.4 yarn still uses a different name (or the mapping build number doesn't exist), the mixin will hard-fail at load (defaultRequire: 1). Pinned versions in gradle.properties: yarn=1.21.4+build.8, loader=0.16.9, fabric_api=0.114.0+1.21.4, loom=1.9-SNAPSHOT — please confirm these resolve.
• In-game smoke test: install Fabric 1.21.4 + Fabric API + this mod, jump from ≥3 blocks onto a group of mobs holding a Mace, confirm (a) primary target still takes vanilla smash damage, (b) neighbors within radius take reduced damage and get pushed outward, (c) no double-damage on the primary target, (d) nothing fires when you hit on flat ground.
• Verify Minecraft API surface used by the mixin matches 1.21.4 yarn: LivingEntity#damage(ServerWorld, DamageSource, float), EntityType#create(ServerWorld, SpawnReason), LightningEntity#setCosmetic / setChanneler / refreshPositionAfterTeleport, Entity#velocityModified field, ServerWorld#getEntitiesByClass. If any of these were renamed in 1.21.4 yarn, the mixin won't compile.
• Sanity-check this even belongs in kinngg2/DeepSeek-Math — this repo is a Python ML research project; a Minecraft mod is a topical mismatch. If you wanted it in a different repo, say the word and I'll move it.

Notes

• The bonus-damage formula (4/2/1 per block for 0–3 / 3–8 / 8+) is a reconstruction of vanilla, not a re-use of MaceItem.getBonusAttackDamage. If vanilla's exact thresholds differ in 1.21.4, the AOE damage numbers will drift slightly from "ideal."
• Neighbors only receive the AOE-scaled bonus; they do not receive a "base" mace hit, so primary-target damage is never duplicated.
• MaceItemMixin.java has an unused import net.minecraft.entity.Entity; — harmless warning, easy follow-up cleanup.
• No Forge/NeoForge variant is included (README explains; would require Architectury or a parallel loader project).
• No LICENSE file is present in the mod subdirectory, but build.gradle references one in jar { from("LICENSE") ... } — the from will silently no-op if the file is absent, but you may want to add one or remove that block.

Link to Devin session: https://app.devin.ai/sessions/fa8c614cc631433a9d395c4426214190
Requested by: @kinngg2

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