A House-Senate conference committee this week agreed to give the FHA authority to insure so-called hybrid ARMs, along with a sizable bump in budget authority for the Office of Federal Housing Enterprise Oversight, the safety-and-soundness regulator of Fannie Mae and Freddie Mac. Mortgage bankers have been lobbying for an FHA program to insure adjustable-rate mortgages that have initial periods of fixed interest rates of three years or more. These products have become a mainstay in