The Dow reached another milestone, recording its longest winning streak since 1996 after it rose for the 10th straight day. ‘‘It’s just a good run,’’ said one observer. ‘‘And it speaks to optimism about the future,’’ he added. Encouraging jobs news that fewer Americans sought unemployment benefits gave markets an early lift. Record corporate profits and reassurances from Fed officials that they plan to keep interests rates low have also helped push stocks higher. Thursday was a big day for retailers — Coldwater Creek jumped after it posted a smaller-than-expected loss. And Men’s Wearhouse soared on news it would consider selling its K&G unit.