A regulatory agreement between the Federal Home Loan Bank of Seattle and the Federal Housing Finance Board has put the FHLBank’s prospective MBS program on hold and could scuttle its mortgage purchase business for good. Seattle officials signed an agreement late last week that directs them to devise an overall business plan by Feb. 28, and to hire outside consultants to review the risk-management policies and governance at the government-sponsored enterprise. FHFB officials said they…