知识库indexing构建索引卡住了 跑不动

**Describe the bug**

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**To Reproduce**

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1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

**Expected behavior**

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**Version:**

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**Environment:**

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**Additional context**

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No file, test, version, environment, or reproducible step is provided. First obtain those details and locate the knowledge-base indexing entry point; confirm the hang can be reproduced before changing anything. Done means indexing completes or reports a clear failure, with a regression test if the relevant test location is identified.

Written by the indexing model from the issue text.