Title: Feature Request: "Zombie Apocalypse / Ruined World" Generation Preset

Description: It would be awesome to have a built-in generation preset or toggle for a post-apocalyptic / ruined environment without needing external mods. Since Arnis generates .mca files directly, it could apply decay algorithms and block replacements during creation. Suggested Features: Block Decay & Damage: Automatically replace a percentage of clean blocks with damaged/mossy variants (e.g., stone_bricks -> cracked_stone_bricks / mossy_stone_bricks), randomly remove glass blocks, and add cobwebs/vines to walls. Loot Generation: Automatically place chests inside buildings on floor blocks using vanilla loot tables (e.g., minecraft:chests/abandoned_mineshaft or minecraft:chests/simple_dungeon). Ruined Infrastructure: Replace sections of roads/asphalt with coarse dirt, gravel, or water to simulate abandoned, overgrown streets.