Map overlap GPUs through infer placement

[TianyeGGBond]

Context

_wait_for_overlap_engines_offloaded receives physical GPU IDs from the scheduler, while the rollout manager expects local engine indices within the pipeline's inference placement. The previous conversion assumed the inference GPUs were contiguous and derived engine indices by subtracting the first GPU ID.

Change

• add _resolve_overlap_infer_engines under the file's Helpers section
• resolve overlapping train GPUs through the configured actor_infer placement
• return explicit overlap_engine_indices and overlap_gpu_ids for the wait logic
• reject inference mappings whose length is not divisible by rollout_num_gpus_per_engine

Validation

• python -m py_compile rlix/pipeline/miles_pipeline.py
• git diff --check