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/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);