fix: 缓存直接写+fsync，去掉会误删的写后校验

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

代码/code/bench.py

@@ -129,21 +129,17 @@ def _save_cache(cache, item_dict, user_seq):
     读取会间歇性报 [Errno 38]。pickle.dump 大对象较慢但顺序写更稳。
     """
     import pickle
-    tmp = str(cache) + ".tmp"
     try:
-        with open(tmp, "wb") as f:
+        with open(cache, "wb") as f:
             pickle.dump({"item_dict": item_dict, "user_seq": user_seq}, f,
                         protocol=pickle.HIGHEST_PROTOCOL)
             f.flush()
             os.fsync(f.fileno())
-        os.replace(tmp, cache)
-        _load_cache(cache)  # 写后立即校验可读
-        print(f"[BENCH] 已缓存 -> {cache}")
+        print(f"[BENCH] 已缓存 -> {cache}（下次秒级读取；读不出会自动重建）")
     except Exception as e:
         print(f"[BENCH][WARN] 缓存写入失败（{e}），本次不缓存（不影响结果）")
-        for p in (tmp, str(cache)):
         try:
-                os.remove(p)
+            os.remove(cache)
         except OSError:
             pass