Clean repo for open source release

Remove build artifacts, dev tool configs, unused dependencies,
and third-party source dumps. Add proper README, update .gitignore,
clean up Makefile.

src/main/java/com/tiedup/remake/entities/MerchantTrade.java

@@ -0,0 +1,137 @@
+package com.tiedup.remake.entities;
+
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.network.chat.Component;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+
+/**
+ * Represents a single trade offer from a Kidnapper Merchant.
+ *
+ * Price is in gold ingots and/or gold nuggets.
+ * Example: 3x Gold Ingot + 5x Gold Nugget for 1x Ropes
+ */
+public class MerchantTrade {
+
+    private final ItemStack item;
+    private final int ingotPrice;
+    private final int nuggetPrice;
+
+    public MerchantTrade(ItemStack item, int ingotPrice, int nuggetPrice) {
+        this.item = item.copy();
+        this.ingotPrice = Math.max(0, ingotPrice);
+        this.nuggetPrice = Math.max(0, nuggetPrice);
+    }
+
+    /**
+     * Check if the player can afford this trade with the given stacks.
+     *
+     * @param ingots Stack of gold ingots (or empty)
+     * @param nuggets Stack of gold nuggets (or empty)
+     * @return true if player has enough gold
+     */
+    public boolean canAfford(ItemStack ingots, ItemStack nuggets) {
+        int ingotCount = ingots.is(Items.GOLD_INGOT) ? ingots.getCount() : 0;
+        int nuggetCount = nuggets.is(Items.GOLD_NUGGET)
+            ? nuggets.getCount()
+            : 0;
+
+        return ingotCount >= ingotPrice && nuggetCount >= nuggetPrice;
+    }
+
+    /**
+     * Consume the payment from the given stacks.
+     * MUST call canAfford() before this!
+     *
+     * @param ingots Stack of gold ingots
+     * @param nuggets Stack of gold nuggets
+     */
+    public void consumePayment(ItemStack ingots, ItemStack nuggets) {
+        if (ingots.is(Items.GOLD_INGOT)) {
+            ingots.shrink(ingotPrice);
+        }
+        if (nuggets.is(Items.GOLD_NUGGET)) {
+            nuggets.shrink(nuggetPrice);
+        }
+    }
+
+    /**
+     * Get the item being sold.
+     * @return Copy of the item stack
+     */
+    public ItemStack getItem() {
+        return item.copy();
+    }
+
+    /**
+     * Get display name of the item.
+     */
+    public Component getItemName() {
+        return item.getHoverName();
+    }
+
+    /**
+     * Get ingot price.
+     */
+    public int getIngotPrice() {
+        return ingotPrice;
+    }
+
+    /**
+     * Get nugget price.
+     */
+    public int getNuggetPrice() {
+        return nuggetPrice;
+    }
+
+    /**
+     * Get formatted price display.
+     * Examples:
+     * - "5 gold + 12 nuggets"
+     * - "3 gold"
+     * - "8 nuggets"
+     */
+    public Component getPriceDisplay() {
+        if (ingotPrice > 0 && nuggetPrice > 0) {
+            return Component.literal(
+                ingotPrice + " gold + " + nuggetPrice + " nuggets"
+            );
+        } else if (ingotPrice > 0) {
+            return Component.literal(ingotPrice + " gold");
+        } else if (nuggetPrice > 0) {
+            return Component.literal(nuggetPrice + " nuggets");
+        } else {
+            return Component.literal("Free");
+        }
+    }
+
+    /**
+     * Save this trade to NBT.
+     */
+    public CompoundTag save() {
+        CompoundTag tag = new CompoundTag();
+        tag.put("Item", item.save(new CompoundTag()));
+        tag.putInt("IngotPrice", ingotPrice);
+        tag.putInt("NuggetPrice", nuggetPrice);
+        return tag;
+    }
+
+    /**
+     * Load a trade from NBT.
+     */
+    public static MerchantTrade load(CompoundTag tag) {
+        ItemStack item = ItemStack.of(tag.getCompound("Item"));
+        int ingotPrice = tag.getInt("IngotPrice");
+        int nuggetPrice = tag.getInt("NuggetPrice");
+        return new MerchantTrade(item, ingotPrice, nuggetPrice);
+    }
+
+    @Override
+    public String toString() {
+        return (
+            item.getHoverName().getString() +
+            " for " +
+            getPriceDisplay().getString()
+        );
+    }
+}