Anne Midgette: The news last night was Christine Goerke. At 9:30 Monday morning, the Washington National Opera announced that America’s reigning Wagner soprano would be making a last-minute substitution for Catherine Foster, who had injured her leg during the dress rehearsal a week before, in that night’s premiere of “Die Walküre,” the second opera in Wagner’s “Ring” cycle. Goerke, who had just sung “Siegfried” in Houston on Sunday, arrived, slipped into costume and delivered some of the best Wagner singing I can recall, making a regal, gleaming Brünnhilde as the centerpiece to a memorable night.