orcarouter_chat
Send a single-turn chat request to OrcaRouter and return the assistant's response text. Default model is the workspace's auto-router. Use orcarouter/<name> for other routers or <provider>/<model> for direct calls. For OpenAI reasoning models (gpt-5/o1/o3/...), max_tokens is automatically routed to max_completion_tokens at the wire level. The optional models array sets a fallback chain — the primary model is tried first, then each entry on failure (5 entries total max, including the primary). Errors are returned as text content with isError:true; common cases include missing API key, rate limits, and upstream provider outages. Requires ORCAROUTER_API_KEY.