Prime Minister Benjamin Netanyahu of Israel said Friday that the military had advanced deeper into Lebanon, where Israel and Hezbollah have continued to trade attacks, further undermining a monthlong cease-fire that has done little to stem the fighting. Speaking in the north of Israel, near the Lebanese border, while visiting troops, Mr. Netanyahu said Israeli forces had “crossed the Litani,” a river that has long been a demarcation line in cease-fire arrangements in southern Lebanon. Israel