Two companies’ seasons end this weekend with a number of stars continuing runs of important works. Austria The Wiener Staatsoper will showcase Debussy’s “Pelléas et Mélisande” starring Franz-Josef Selig, Bernarda Fink, Adrian Eröd, Simon Keenlyside and Olga Bezsmertna ending the season. Czech Republic The Prague Summer Nights festival continues with Opera scenes and the opening of   Mozart’s “Die Zauberflöte.” {…}