fix(distributed): default LOCAL_RANK to 0 instead of 1 in run.py

[Xayar145]

Description

Fixes LOCAL_RANK default value in run.py:

• In run.py, LOCAL_RANK was defaulting to 1 (int(os.environ.get("LOCAL_RANK", 1))), whereas RANK defaults to 0, WORLD_SIZE defaults to 1, and LOCAL_WORLD_SIZE defaults to 1.
• When launchers or custom multi-process scripts initialize processes without explicitly exporting LOCAL_RANK for rank 0, process 0 calculated DEVICE_START_IDX = GPU_PER_PROC * 1 instead of 0, binding to GPU 1 and causing device collision.
• Fixed the default value to 0, matching standard distributed environment conventions.