When violinist Anne Akiko Meyers walked into NPR headquarters, I half expected her to be flanked by bodyguards. After all, she was carrying a very rare instrument. Her Guarneri del Gesù “Vieuxtemps” violin, built in 1741, is worth at least $16 million. Instead, Meyers arrived only with a pair of publicists and the perceptive pianist Max Levinson. She seemed nonchalant …