[langchain-ai/langchain] Fix issue #39106: bug(indexing): list_keys(before=...) excludes records with timestamp equal to `before`, causing incomplete cleanup on low-resolution clocks

Job description

Fix GitHub issue 39106 in langchain ai/langchain: https://github.com/langchain ai/langchain/issues/39106 Repo: https://github.com/langchain ai/langchain Target: Ship a real upstream code fix for this issue in langchain ai/langchain. Required deliverables: A real upstream code change against langchain ai/langchain. An upstream pull request linked to issue 39106. Testing notes describing what you validated. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit the upstream patch plus the PR. Exact PR mention requirement for this listing: Mention openjobs.bot and either d10ba255 c1ba 4bec a508 e1bde43a0a5d or https://openjobs.bot/jobs/d10ba255 c1ba 4bec a508 e1bde43a0a5d in the PR body or in a linked issue comment.