CobbleStacker

Bug fix — Watchdog crash (ItemStackManager.java):

• processAutoClear and forceClear were calling item.discard() while iterating level.getAllEntities() (a live iterable), causing a ConcurrentModificationException that froze the server thread. Both methods now collect entities into a toRemove list first, then discard after iteration.

Feature — Mob nametag visibility distance (3 files):

• ModConfig.java: Added mobNametagVisibleDistance (default 0 = always visible, like current behavior). Set it to e.g. 32 to only show nametags within 32 blocks.
• MobStackManager.java:
  • updateNametag no longer forces setCustomNameVisible(true) when distance mode is active
  • New updateNametagVisibility(server) method checks each stacked mob against all players in the level and toggles visibility based on squared distance
• CobbleStackerMod.java: Calls updateNametagVisibility every 10 ticks (0.5s) when distance mode is enabled