The oil market still looks surprisingly calm for a system that has spent nearly three months absorbing the largest supply disruption in modern history. That should probably make people nervous. Because underneath the headline inventory numbers, the market has gone from adding barrels to burning through them. And lately, it has been using emergency reserves to help keep the machinery running. The inventory picture still looks comfortable if you zoom out far enough. According to Oilprice.com's analysis of weekly API data, U.S. commercial crude inventories…