After turning down a “reasonable” offer from the owners of the bike shop that used to occupy the ground floor, the seller of 147 Union Street in the Columbia Waterfront District has gone into contract for $1 million, according to Realty Collective. That’s $100,000 less than the asking price on the three-story building. Meanwhile, the bike shop has decamped to 514 Court Street and 147 Union will soon have an insurance brokerage. GMAP