WASHINGTON — The Pentagon’s plan outlining the long-stalled effort to close the Guantanamo Bay detention center, expected in the coming week, includes details suggesting that the Centennial Correctional Facility in Colorado is one suitable site to send detainees whom officials believe should never be released, administration officials said. The plan represents a last-gasp effort by the Obama administration to convince staunch opponents in Congress that dangerous detainees who can’t be transferred safely to other countries should be housed in a U.S.-based prison. According to administration officials, the plan makes no recommendations on which of seven U.S.