surface comm overlap rank errors

[sudhakarsingh27]

Description

Please include a brief summary of the changes, relevant motivation and context.

Fixes # (issue)

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Changes

Please list the changes introduced in this PR:

• Change A
• Change B

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[greptile-apps]

Greptile Summary

The PR improves failure reporting for distributed communication-overlap tests and isolates subprocess-specific environment overrides.

• Records rank-level exceptions in the distributed layer runner.
• Centralizes subprocess result validation with bounded stdout and stderr diagnostics.
• Prevents test-specific environment settings from leaking between parametrized cases.
• Disables FlashAttention v4 at the distributed QA suite boundary.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains within the eligible follow-up-review scope.

No blocking failure remains.

Important Files Changed

Filename	Overview
qa/L1_pytorch_distributed_unittest/test.sh	Moves the FlashAttention v4 disablement to a suite-wide export and removes redundant per-command assignments.
tests/pytorch/distributed/run_layer_with_overlap.py	Adds Torch Elastic exception recording so distributed rank failures provide structured diagnostics.
tests/pytorch/distributed/test_comm_gemm_overlap.py	Adds centralized subprocess validation, text-mode output capture, bounded diagnostics, and isolated child-process environments.

_{Reviews (2): Last reviewed commit: "Keep FA4 out of L1 distributed tests" | Re-trigger Greptile}

[sudhakarsingh27]

/te-ci pytorch L1