Market-tick prices new NPC listings from the economy ledger (base x priceModifier, vendor modifier applied) instead of the old autoPrice +/-15% randomness, and scales restock quantity down under shortage. buyListing records real demand from completed purchases of NPC/vendor stock.
Ultraworked with [Sisyphus](https://github.com/code-yeongju/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
