fix: 稳定并发 worker 回归测试

infrastructure/src/downloader.rs

@@ -221,6 +221,11 @@ mod tests {
                     thread::sleep(Duration::from_millis(20));
                     self.active.fetch_sub(1, Ordering::SeqCst);
                 } else {
+                    if task == 1 {
+                        while self.active.load(Ordering::SeqCst) == 0 {
+                            thread::yield_now();
+                        }
+                    }
                     if task == 2 && self.active.load(Ordering::SeqCst) > 0 {
                         self.task_two_started_while_task_zero_active
                             .fetch_add(1, Ordering::SeqCst);