GOYANG, South Korea — The leaders of North and South Korea made bold pledges Friday to work toward a “common goal” of denuclearizing their peninsula and formally ending the Korean War by the end of this year, following a historic day of talks on the border that has divided them for almost seven decades.It was a day marked by an astonishing level of congeniality between the two, including a warm embrace at the signing of the “Panmunjeom Declaration,” named after the truce village in the Demilitarized Zone where it was forged.It was, however, short on details as to what “denuclearization” means for each of them.Still, the fact that Kim Jong Un and Moon Jae-in spent so much time together — and came up with a joint statement that even includes the word “denuclearization” — marked a surprising development after a year of threats and missile launches that brought the specter of war back to the Korean Peninsula.“This provides the political space for Trump to have his own summit with Kim,” said Duyeon Kim, a visiting fellow at the Korean Peninsula Future Forum in Seoul.