release(langchain): 1.3.0a2

[Sydney Runkle (sydney-runkle)]

Bumps langchain from 1.3.0a1 → 1.3.0a2. Also locks langgraph==1.2.0a7 / langgraph-checkpoint==4.1.0a4 and adds prerelease = "allow" to [tool.uv] so the resolver picks up transitive alpha deps automatically.

[codspeed-hq]

Merging this PR will not alter performance

✅ 2 untouched benchmarks
⏩ 13 skipped benchmarks¹

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_{Comparing sr/release-langchain-1.3.0a2 (8048a03) with master (2ca920c)²}

Footnotes

1. 13 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on v1.4 (2691a6e) during the generation of this report, so master (2ca920c) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩