test(langchain): Add text completion test #5740

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✅ Completed bug detection (2m 36s)
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Final Result: Bugbot completed review and found 1 potential issue.

Request ID: serverGenReqId_ab8992f6-1ce0-43a5-8b27-36acf94d99c5

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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