Smithing Progression

support for The block keeps ticking simulates elapsed time:
- Clay Kilns catch up their smelting, including partial progress. They still require heat and stop when the output slot is full or contains an incompatible item.
- Smoker Racks catch up their upper smoking slots and produce each loaded item once.
 
Zombies and reinforcements.
- Default cap: 15 living nearby zombies, counting the caller, natural zombies and previous reinforcements
- At 14 zombies, a call can add only one.
- At 15 or more, calls add none.
- Several nearby zombies calling at the same time share the remaining capacity.
- The counting area uses the existing ally radius—32 blocks by default.
- Existing zombies remain, and natural spawning can still take the population above 15.