[JAX] Fix classification of sync-tagged collective start instructions

[KshitijLakhani]

Description

Fix JAX collective-byte accounting when XLA emits an all-reduce-start instruction with "is_sync":true.
The parser previously treated this as an unsuffixed synchronous collective and classified the communication bytes as other. This change prioritizes the explicit *-start instruction form.

No LayerNorm/RMSNorm implementation or expected byte calculations are changed.

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

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 fixes JAX distributed-test collective accounting by prioritizing explicit *-start instructions over overlapping "is_sync":true metadata.

• Classifies direct and wrapped asynchronous collective starts before synchronous collectives.
• Preserves ROOT-prefix handling and unsuffixed synchronous collective detection.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
tests/jax/distributed_test_base.py	Reorders collective classification so sync-tagged *-start instructions use the asynchronous-start identification path; no eligible follow-up defect was established.

_{Reviews (2): Last reviewed commit: "[JAX] Fix sync-tagged collective start c..." | Re-trigger Greptile}

[KshitijLakhani]

/te-ci jax L0 L1

[jberchtold-nvidia]

LGTM pending CI, thanks!