[DEBUG DO NOT REVIEW] reproduce CI issues with additional print statements

[igorts-git]

This commit introduces a JAX DPO correctness integration test that validates JAX DPO training step metrics (loss, margin, chosen/rejected logprobs) against stored golden outputs. It also includes the CPU-only JAX/PyTorch parallel validation script used to verify parity against Hugging Face TRL and generate the remote-canonical golden assets.

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[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/trainers/post_train/dpo/train_dpo.py	66.66%	1 Missing and 1 partial ⚠️

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