Honor executor srun_args for Ray COMMAND srun

[hemildesai]

Summary

• remove hardcoded permanent args from the Ray COMMAND launch srun path in ray.sub.j2
• pass command_srun_args from SlurmRayRequest so launch args come from executor config (executor.srun_args)
• for heterogeneous grouped runs, use resource_group[0].srun_args for the head/COMMAND launch path
• add regression coverage to verify the generated COMMAND srun honors executor srun_args

Testing

• uv run pytest test/run/ray/test_slurm_ray_request.py -q

[athitten]

LGTM, thank you @hemildesai !