fix(logic): isolate atomic batch counters and token sync fields

tests/test_batch_task_manager.py

@@ -0,0 +1,21 @@
+from concurrent.futures import ThreadPoolExecutor
+
+from src.web.task_manager import task_manager
+
+
+def test_record_batch_task_result_is_atomic_under_threads():
+    batch_id = "batch-atomic-test"
+    task_manager.init_batch(batch_id, 100)
+
+    statuses = ["completed"] * 60 + ["failed"] * 40
+
+    with ThreadPoolExecutor(max_workers=16) as executor:
+        list(executor.map(lambda status: task_manager.record_batch_task_result(batch_id, status), statuses))
+
+    snapshot = task_manager.get_batch_status(batch_id)
+
+    assert snapshot is not None
+    assert snapshot["completed"] == 100
+    assert snapshot["success"] == 60
+    assert snapshot["failed"] == 40
+    assert snapshot["skipped"] == 0