Touting the start of a new era in Somerville, local and state officials broke ground last week at Assembly Row, the complex of stores and apartments that planners say will transform a long-disused industrial space into a bustling neighborhood. When completed in 2014, the complex will hold 2,050 units of housing, a 200-room hotel, shops, a movie theater, and an Orange Line T station. The first phase of construction will raise the 195-unit Avalon at Assembly Row building. At a dusty news conference held at the heart of the 45-acre site, where crews already were busy surveying and drilling for the buildings' foundations, members of state government made their pitch for casting Assembly Square as the mold for development in Massachusetts. Through a program launched in 2008, the state helped finance $25 million worth of infrastructure improvements that included the construction of wider roads, laying of underground water and sewer pipe, and installation of new traffic signals. The former home of a Ford plant that assembled Edsel cars, the parcel is now one of largest brownfield sites in the state set to be fully redeveloped, said Philip Griffiths, state undersecretary for environment. Also expected to go forward in the project's first phase is a planned 6-acre park that hugs the waterfront property line on the Mystic River. Work on the Assembly Square Orange Line T station that will connect the new neighborhood to downtown Boston is expected to be complete by 2014 to coincide with the complex's opening.