单机模式下只有一个线程处理数据，node_id从0开始映射成graph_builder输出的Node Count不是应该和节点数量相等吗？

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The issue identifies single-machine mode, one data-processing thread, node_id mapping from 0, and graph_builder's Node Count, but names no files or tests. Reproduce the reported behavior in single-machine mode and trace those values to determine whether Node Count matches the number of nodes; done means the discrepancy is explained and a concrete fix or confirmed expected behavior is documented.

Written by the indexing model from the issue text.