nrouter - OpenAI-Compatible SDK for the nRouter LLM Gateway

A client for the nRouter LLM gateway (<https://nrouter.ai>), an OpenAI-compatible API giving one key access to models across six provider clouds. No official OpenAI SDK exists for R, so this package calls the HTTP API directly via 'httr'. Gateway refusals are raised as classed conditions, and per-request cost and token metadata are returned alongside every response.