unify folder naming with resolved audio profiles across providers

internal/provider/qobuz/client_test.go

@@ -366,6 +366,9 @@ func TestGetDownloadableUsesReturnedURLExtension(t *testing.T) {
 	if d.Extension != "mp3" {
 		t.Fatalf("extension = %q, want mp3", d.Extension)
 	}
+	if d.Audio.Container != "MP3" || d.Audio.Codec != "MP3" {
+		t.Fatalf("unexpected audio profile: %+v", d.Audio)
+	}
 }
 
 func qobuzSecretSig(requestTS, secret string) string {