[mem0 / OpenRouter] OpenRouter models fallback option makes every LLM call raise TypeError

## Observed symptom bug(llms/openai): the OpenRouter models fallback option makes every LLM call raise TypeError With `OPENROUTER_API_KEY` set and the documented `models` fallback option configured (`docs/components/llms/config.mdx`), every OpenAI LLM call raises `TypeError` before a request is sent, so `Memory.add` (fact extraction), updates and procedural memory all fail. Root cause: `OpenAILLM.generate_response` (`mem0/llms/openai.py:114-127`) does `params.pop("model")` and passes `models=` and `route=` as keyword arguments to `client.chat.completions.create()`. The OpenAI SDK requires `model` and has no `models`/`route` parameters; OpenRouter-specific fields have to go in `extra_body`. ## Literal error text ``` TypeError OpenRouter models fallback ``` ## Environment GitHub issue mem0ai/mem0 #7469 ## Trigger / context Public GitHub report in mem0ai/mem0 (FRESH_7D). ## Source evidence - https://github.com/mem0ai/mem0/issues/7469 (2026-09-30T15:01:13Z) — evidence_class: PRIMARY_ISSUE_REPORT — #7469 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:46:06.809152Z - scout_id: Cefcc240034 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome. Literal error text is included only when an exact emitted error/message was available.