Adjustable-rate mortgages and so-called nontraditional loan products continued to comprise a substantial portion of the primary market originations during the first quarter of 2006, according to a new market analysis and ranking by Inside Mortgage Finance. Despite a flat yield curve that squeezes the payment advantage of adjustable-rate mortgages relative to fixed-rate products, lenders originated a healthy $282 billion of ARMs during the first three months of 2006. That represented 42.1 percent of total…