vllm-0001: punica_wrapper/utils.py convert_mapping() calls
lora_index_to_id.index(x) per token in batch — O(B*L) where
B=batch_size, L=loaded_loras. Code has "TODO index can be slow"
comment. Fix: pre-build dict for O(1) lookup. 7x at B=2000/L=64.
Ollama: all slices.Contains on bounded slices (1-8 items).
LangChain: orchestration code, all membership bounded by k param.
