fix: clean up merge temp dir on export failure

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/src/commands/export.rs

@@ -88,15 +88,16 @@ pub async fn export_clips(
                         .unwrap_or(std::cmp::Ordering::Equal)
                 });
 
-                clip_exporter::export_merged(
+                let temp_dir_str = temp_dir.to_string_lossy().to_string();
+                let merge_result = clip_exporter::export_merged(
                     &sorted_clips,
                     &config.source_file_path,
                     &output,
                     &config.cut_mode,
-                    &temp_dir.to_string_lossy(),
-                )?;
-
+                    &temp_dir_str,
+                );
                 let _ = std::fs::remove_dir_all(&temp_dir);
+                merge_result?;
 
                 let paths = vec![output];
                 let _ = on_event.send(ExportEvent::Finished {