NEW YORK — Leslie Holm has no trouble pulling together a big-time performance. She spent 19 years as a lighting technician and electrician on tours by acts ranging from Beyonce to Bon Jovi. But guiding her dog, Riley Nico, through the Westminster Kennel Club agility competition? “This gives me butterflies,” Holm says. She never envisioned herself doing something like this before adopting the mixed-breed dog and seeing her jump over benches and weave around people at a pooch park. Three years later, in her first turn Saturday at the nation’s most famous dog show, Riley Nico finished racking up points to be at the “master agility champion” level. But Holm says the biggest reward isn’t a ribbon or title — it’s a connection. “You’re teammates.