feat(D-01/A): interaction routing + TyingInteractionHelper (A8)

- DataDrivenBondageItem.use(): shift+click cycles bind mode for ARMS items
- DataDrivenBondageItem.interactLivingEntity(): region-based routing
  - ARMS → TyingInteractionHelper (tying task with progress bar)
  - NECK → deferred to Branch C (no V2 collar JSONs yet)
  - Other regions → instant equip via parent AbstractV2BondageItem
- TyingInteractionHelper: extracted tying flow using V2TyingPlayerTask
  - Distance/LoS validation, swap if already tied, task lifecycle

src/main/java/com/tiedup/remake/v2/bondage/TyingInteractionHelper.java

@@ -0,0 +1,107 @@
+package com.tiedup.remake.v2.bondage;
+
+import com.tiedup.remake.core.SettingsAccessor;
+import com.tiedup.remake.core.TiedUpMod;
+import com.tiedup.remake.state.IBondageState;
+import com.tiedup.remake.state.PlayerBindState;
+import com.tiedup.remake.tasks.TyingTask;
+import com.tiedup.remake.tasks.V2TyingPlayerTask;
+import com.tiedup.remake.util.KidnappedHelper;
+import com.tiedup.remake.v2.BodyRegionV2;
+import com.tiedup.remake.v2.bondage.capability.V2EquipmentHelper;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+
+/**
+ * Handles the tying interaction flow for V2 data-driven ARMS items.
+ *
+ * <p>Extracted from {@code ItemBind.interactLivingEntity()} to support
+ * the same tying task flow for data-driven items.</p>
+ */
+public final class TyingInteractionHelper {
+
+    private TyingInteractionHelper() {}
+
+    /**
+     * Handle right-click tying of a target entity with a V2 ARMS item.
+     * Creates/continues a V2TyingPlayerTask.
+     */
+    public static InteractionResult handleTying(
+        ServerPlayer player,
+        LivingEntity target,
+        ItemStack stack,
+        InteractionHand hand
+    ) {
+        IBondageState targetState = KidnappedHelper.getKidnappedState(target);
+        if (targetState == null) return InteractionResult.PASS;
+
+        // Kidnapper can't be tied themselves
+        IBondageState kidnapperState = KidnappedHelper.getKidnappedState(player);
+        if (kidnapperState != null && kidnapperState.isTiedUp()) {
+            return InteractionResult.PASS;
+        }
+
+        // Already tied — try to swap
+        if (targetState.isTiedUp()) {
+            if (stack.isEmpty()) return InteractionResult.PASS;
+            ItemStack oldBind = V2EquipmentHelper.unequipFromRegion(target, BodyRegionV2.ARMS);
+            if (!oldBind.isEmpty()) {
+                V2EquipmentHelper.equipItem(target, stack.copy());
+                stack.shrink(1);
+                target.spawnAtLocation(oldBind);
+                TiedUpMod.LOGGER.debug("[TyingInteraction] Swapped bind on {}", target.getName().getString());
+                return InteractionResult.SUCCESS;
+            }
+            return InteractionResult.PASS;
+        }
+
+        // Distance + line-of-sight (skip for self-tying)
+        boolean isSelfTying = player.equals(target);
+        if (!isSelfTying) {
+            if (player.distanceTo(target) > 4.0 || !player.hasLineOfSight(target)) {
+                return InteractionResult.PASS;
+            }
+        }
+
+        // Create/continue tying task
+        PlayerBindState playerState = PlayerBindState.getInstance(player);
+        if (playerState == null) return InteractionResult.PASS;
+
+        int tyingSeconds = SettingsAccessor.getTyingPlayerTime(player.level().getGameRules());
+
+        V2TyingPlayerTask newTask = new V2TyingPlayerTask(
+            stack.copy(),
+            stack,
+            targetState,
+            target,
+            tyingSeconds,
+            player.level(),
+            player
+        );
+
+        TyingTask currentTask = playerState.getCurrentTyingTask();
+        if (currentTask == null
+            || !currentTask.isSameTarget(target)
+            || currentTask.isOutdated()
+            || !ItemStack.matches(currentTask.getBind(), stack)) {
+            playerState.setCurrentTyingTask(newTask);
+            newTask.start();
+        } else {
+            newTask = (V2TyingPlayerTask) currentTask;
+        }
+
+        newTask.update();
+
+        if (newTask.isStopped()) {
+            stack.shrink(1);
+            playerState.setCurrentTyingTask(null);
+            TiedUpMod.LOGGER.info("[TyingInteraction] {} tied {}", player.getName().getString(), target.getName().getString());
+        }
+
+        return InteractionResult.SUCCESS;
+    }
+}

src/main/java/com/tiedup/remake/v2/bondage/datadriven/DataDrivenBondageItem.java

@@ -1,7 +1,10 @@
 package com.tiedup.remake.v2.bondage.datadriven;
 
+import com.tiedup.remake.core.TiedUpMod;
 import com.tiedup.remake.v2.BodyRegionV2;
+import com.tiedup.remake.v2.bondage.BindModeHelper;
 import com.tiedup.remake.v2.bondage.IV2BondageEquipment;
+import com.tiedup.remake.v2.bondage.TyingInteractionHelper;
 import com.tiedup.remake.v2.bondage.V2BondageItems;
 import com.tiedup.remake.v2.bondage.capability.V2EquipmentHelper;
 import com.tiedup.remake.v2.bondage.component.ComponentHolder;
@@ -17,7 +20,13 @@ import java.util.stream.Collectors;
 import net.minecraft.ChatFormatting;
 import net.minecraft.network.chat.Component;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundEvents;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.InteractionResultHolder;
 import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.TooltipFlag;
 import net.minecraft.world.level.Level;
@@ -116,6 +125,55 @@ public class DataDrivenBondageItem extends AbstractV2BondageItem {
         return def != null && def.supportsColor();
     }
 
+    // ===== INTERACTION ROUTING =====
+
+    @Override
+    public InteractionResultHolder<ItemStack> use(Level level, Player player, InteractionHand hand) {
+        ItemStack stack = player.getItemInHand(hand);
+        Set<BodyRegionV2> regions = getOccupiedRegions(stack);
+
+        // ARMS items: shift+click cycles bind mode
+        if (regions.contains(BodyRegionV2.ARMS) && player.isShiftKeyDown() && !level.isClientSide) {
+            BindModeHelper.cycleBindModeId(stack);
+            player.playSound(SoundEvents.CHAIN_STEP, 0.5f, 1.2f);
+            player.displayClientMessage(
+                Component.translatable(
+                    "tiedup.message.bindmode_changed",
+                    Component.translatable(BindModeHelper.getBindModeTranslationKey(stack))
+                ),
+                true
+            );
+            return InteractionResultHolder.success(stack);
+        }
+        return super.use(level, player, hand);
+    }
+
+    @Override
+    public InteractionResult interactLivingEntity(
+        ItemStack stack, Player player, LivingEntity target, InteractionHand hand
+    ) {
+        // Client: arm swing
+        if (player.level().isClientSide) {
+            return InteractionResult.SUCCESS;
+        }
+
+        DataDrivenItemDefinition def = DataDrivenItemRegistry.get(stack);
+        if (def == null) return InteractionResult.PASS;
+
+        Set<BodyRegionV2> regions = def.occupiedRegions();
+
+        // ARMS: tying flow (do NOT call super — avoids double equip)
+        if (regions.contains(BodyRegionV2.ARMS) && player instanceof ServerPlayer serverPlayer) {
+            return TyingInteractionHelper.handleTying(serverPlayer, target, stack, hand);
+        }
+
+        // NECK: collar equip blocked for now — V2 collar JSONs don't exist in Branch A.
+        // Full collar equip flow (add owner, register, sound) wired in Branch C.
+
+        // All other regions (MOUTH, EYES, EARS, HANDS): instant equip via parent
+        return super.interactLivingEntity(stack, player, target, hand);
+    }
+
     // ===== IHasResistance IMPLEMENTATION =====
 
     @Override