fix: keep export dropdown open on save-failure branches too

GIF save-failure and MP4 save-failure paths had the same bug as the
export-failure paths: dropdown closes hiding the exportError UI. Now
keepExportDialogOpen = true in all non-smoke failure branches.

src/components/video-editor/hooks/editorExportWorkflow.ts

@@ -236,6 +236,7 @@ export async function runEditorExport({
 						window.close();
 						return;
 					}
+					keepExportDialogOpen = true;
 				}
 			} else {
 				setExportError(result.error || "GIF export failed");
@@ -456,6 +457,7 @@ export async function runEditorExport({
 						window.close();
 						return;
 					}
+					keepExportDialogOpen = true;
 				}
 			} else {
 				if (smokeExportConfig.enabled) {