fix(D-01/A): adversarial review fixes — 4 logic bugs

1. NECK region explicitly blocked in interactLivingEntity() — prevents
   V2 collars equipping without ownership setup (latent, no JSONs yet)

2. Swap rollback safety: if re-equip fails after swap failure, drop the
   old bind as item entity instead of losing it silently

3. GaggingComponent: cache GagMaterial at construction time — eliminates
   valueOf() log spam on every chat message with misconfigured material

4. Dual-bind prevention: check both V1 isTiedUp() AND V2 region occupied
   in TyingInteractionHelper and PacketSelfBondage to prevent equipping
   V2 bind on top of V1 bind

src/main/java/com/tiedup/remake/network/selfbondage/PacketSelfBondage.java

@@ -248,8 +248,8 @@ public class PacketSelfBondage {
         IV2BondageItem v2Item,
         IBondageState state
     ) {
-        // Can't self-tie if already tied
-        if (state.isTiedUp()) {
+        // Can't self-tie if already tied (check both V1 state and V2 region to prevent dual-bind)
+        if (state.isTiedUp() || V2EquipmentHelper.isRegionOccupied(player, BodyRegionV2.ARMS)) {
             TiedUpMod.LOGGER.debug("[SelfBondage] {} tried V2 self-tie but already tied", player.getName().getString());
             return;
         }

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

@@ -46,8 +46,8 @@ public final class TyingInteractionHelper {
             return InteractionResult.PASS;
         }
 
-        // Already tied — try to swap
-        if (targetState.isTiedUp()) {
+        // Already tied — try to swap (check both V1 state and V2 region to prevent dual-bind)
+        if (targetState.isTiedUp() || V2EquipmentHelper.isRegionOccupied(target, BodyRegionV2.ARMS)) {
             if (stack.isEmpty()) return InteractionResult.PASS;
             ItemStack oldBind = V2EquipmentHelper.unequipFromRegion(target, BodyRegionV2.ARMS);
             if (!oldBind.isEmpty()) {
@@ -59,8 +59,14 @@ public final class TyingInteractionHelper {
                     return InteractionResult.SUCCESS;
                 } else {
                     // Equip failed — rollback: re-equip old bind
-                    V2EquipmentHelper.equipItem(target, oldBind);
-                    TiedUpMod.LOGGER.debug("[TyingInteraction] Swap failed, rolled back old bind on {}", target.getName().getString());
+                    V2EquipResult rollback = V2EquipmentHelper.equipItem(target, oldBind);
+                    if (!rollback.isSuccess()) {
+                        // Rollback also failed — drop old bind as safety net
+                        target.spawnAtLocation(oldBind);
+                        TiedUpMod.LOGGER.warn("[TyingInteraction] Swap AND rollback failed, dropped old bind for {}", target.getName().getString());
+                    } else {
+                        TiedUpMod.LOGGER.debug("[TyingInteraction] Swap failed, rolled back old bind on {}", target.getName().getString());
+                    }
                     return InteractionResult.PASS;
                 }
             }

src/main/java/com/tiedup/remake/v2/bondage/component/GaggingComponent.java

@@ -23,11 +23,14 @@ import org.jetbrains.annotations.Nullable;
 public class GaggingComponent implements IItemComponent {
 
     private final @Nullable String material;
+    private final @Nullable GagMaterial cachedMaterial;
     private final double comprehensionOverride;
     private final double rangeOverride;
 
-    private GaggingComponent(@Nullable String material, double comprehensionOverride, double rangeOverride) {
+    private GaggingComponent(@Nullable String material, @Nullable GagMaterial cachedMaterial,
+                             double comprehensionOverride, double rangeOverride) {
         this.material = material;
+        this.cachedMaterial = cachedMaterial;
         this.comprehensionOverride = comprehensionOverride;
         this.rangeOverride = rangeOverride;
     }
@@ -47,7 +50,16 @@ public class GaggingComponent implements IItemComponent {
                 range = Math.max(0.0, config.get("range").getAsDouble());
             }
         }
-        return new GaggingComponent(material, comprehension, range);
+        // Resolve and cache GagMaterial at load time to avoid valueOf() on every chat message
+        GagMaterial resolved = null;
+        if (material != null) {
+            try {
+                resolved = GagMaterial.valueOf(material.toUpperCase());
+            } catch (IllegalArgumentException e) {
+                TiedUpMod.LOGGER.warn("[GaggingComponent] Unknown gag material '{}' — using defaults", material);
+            }
+        }
+        return new GaggingComponent(material, resolved, comprehension, range);
     }
 
     /** How much of the gagged speech is comprehensible (0.0 = nothing, 1.0 = full). */
@@ -66,15 +78,9 @@ public class GaggingComponent implements IItemComponent {
         return 10.0;
     }
 
-    /** The gag material enum, or null if not configured or invalid. */
+    /** The gag material enum, or null if not configured or invalid. Cached at load time. */
     public @Nullable GagMaterial getMaterial() {
-        if (material == null) return null;
-        try {
-            return GagMaterial.valueOf(material.toUpperCase());
-        } catch (IllegalArgumentException e) {
-            TiedUpMod.LOGGER.warn("[GaggingComponent] Unknown gag material: {}", material);
-            return null;
-        }
+        return cachedMaterial;
     }
 
     /** The raw material string from JSON, or null. */

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

@@ -167,8 +167,13 @@ public class DataDrivenBondageItem extends AbstractV2BondageItem {
             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.
+        // NECK: blocked until Branch C wires the full collar equip flow
+        // (add owner to NBT, register in CollarRegistry, play sound, sync).
+        // Without this, V2 collars equip without ownership — breaking GPS, shock, alerts.
+        if (regions.contains(BodyRegionV2.NECK)) {
+            TiedUpMod.LOGGER.debug("[DataDrivenBondageItem] NECK equip blocked — collar flow not wired yet");
+            return InteractionResult.PASS;
+        }
 
         // All other regions (MOUTH, EYES, EARS, HANDS): instant equip via parent
         return super.interactLivingEntity(stack, player, target, hand);