[wdykas]

• I, the PR author, have personally reviewed every line of this PR.

Adds an optional process_group to dist_checkpointing.load().

• Uses that group for get_world_size() and all_gather_object().
• Allows each model replica to validate one complete checkpoint view independently.
• Keeps existing behavior unchanged when no group is provided.

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[wdykas]

/ok to test 40d60dd

[svcnvidia-nemo-ci]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/30388732589