Toyota Motor Corp.’s small-car unit, Daihatsu Motor Co., resumed operations at all of its assembly plants in Japan on Tuesday, more than four months after it halted domestic production due to safety test rigging. The automaker restarted production of Copen minivehicles at its main factory in Ikeda, Osaka Prefecture, earlier in the day, the last of its four assembly plants in Japan to resume output. Daihatsu has gradually restarted domestic production since February following a reexamination of its safety standards by the transport ministry, with a shipment ban covering all of its 27 models lif…