Villager trade rebalance experimental (non-imbassive)

This proposal builds on experimental villager trade rework, but in a non‑invasive way. Instead of forcing exclusive trades or locking enchantments to specific biomes, each biome would simply adjust probabilities: higher chances for certain trades related to the biome, and lower chances for others. This subtle balancing improves the experimental system by encouraging exploration and variety, while preserving player freedom and accessibility.