Unify application configuration loading

internal/app/remote_session_test.go

@@ -166,6 +166,9 @@ inputs:
 	if err := loaded.Close(); err != nil {
 		t.Fatalf("second Close() error = %v", err)
 	}
+	if loaded.Config == nil || loaded.Config.Pipeline == nil || loaded.Config.Campaign == nil || loaded.Config.Session == nil {
+		t.Fatal("closing remote session cleanup discarded retained configuration")
+	}
 	if _, err := os.Stat(downloadedPath); !errors.Is(err, os.ErrNotExist) {
 		t.Fatalf("downloaded remote session path still exists or could not be inspected: %q, err=%v", downloadedPath, err)
 	}