If it were announced that “Hamilton” had sparked the single largest day of ticket sales in the history of a long-established theater company, no one would so much as look up from their smartphones. ¶ But “Camelot”? ¶ Yes, “Camelot.” Such was the result for Shakespeare Theatre Company, on the day three weeks ago when reviews appeared for the august Washington troupe’s revival of the 1960 musical by Alan Jay Lerner and Frederick Loewe. The surge in sales not only prompted a week-long extension of the show, to July 8, in the company’s bigger theater, 774-seat Sidney Harman Hall, but the ticket bump also exceeded by 25 percent the previous record, for a 2009 production of “King Lear” starring Stacy Keach, according to company officials.