Add 'Stone Nuggets' & Mineral Sifting to Dirt-Stone Transitions

Currently, the transition between the Overworld dirt layers and solid stone is purely visual. I propose a new mechanic that introduces "Stone Nuggets" packed into this boundary soil, adding depth to early-game survival, combat, and excavation. How to Gather: When a player shovels the very bottom layer of dirt that directly touches stone blocks, it uses a high-reward mineral drop table: • 90% Base Drop: Yields a Stone Nugget alongside the dirt block. • 5% to 10% Rare Drop: Yields an Iron Nugget instead of stone, simulating real-world mineral filtration where heavy iron deposits settle at the bedrock line. Mechanics and Balance: 1. Crafting: Placing 9 Stone Nuggets in a 3x3 crafting grid creates 1 Cobblestone block, allowing players to build up resources passively. 2. Throwable Weapon: Stone Nuggets can be equipped and thrown like snowballs or eggs. Unlike snowballs, their sharp, heavy nature allows them to deal 0.5 to 1 heart of physical damage to mobs. Why this benefits gameplay: • Early Game Lifeline: Gives players trapped in flat, treeless biomes an alternative way to claw their way up to stone tools, while giving them a basic projectile defense weapon before they can craft a bow or sword. • Rewarding Excavation: Makes clearing out large underground basements or terraforming valleys highly satisfying, turning tedious dirt disposal into a passive mining loop.