I may have just seen the biggest interface breakthrough in years. Or not. But I think so?  Things are moving so fast that it’s hard to tell. Ryo Lu, head of design at the white-hot coding tool Cursor has invited me to their charcoal-hued San Francisco studio. Before anyone says hello, I’m greeted by a pile of footwear in the entry of the no-shoes open office. I suddenly regret my choice to wear my New Balance loafers without socks. The softspoken Lu, donning the creative-approved u...