Recurrent Complex Volts

• Improved worldgen performance by avoiding repeated terrain calculations—about 21% faster in the tested Overworld benchmark.
• Fixed terrain filling intended empty spaces inside underground structures.
• Fixed several maze entrance, connector and misplaced child-structure issues.
• Fixed large mazes being cut short or losing pieces when generation queues fill up.
• Fixed unfinished maze pieces being lost after saving and restarting.
• Improved locate responsiveness and added progress updates during searches.

These fixes affect new generation; existing damaged structures are not automatically repaired. Some complex maze connections and slow searches for rare structures remain unresolved.