EN: [Bug] Via Manifest: OpenRouter free models return HTTP 200 with 0 input/output tokens — should trigger autofix or fallback 中文: [Bug] 通过 Manifest 调用 OpenRouter 免费模型：返回 HTTP 200，但 input/output tokens 都为 0 — 应触发 autofix 或 fallback

Set up nanobot to route LLM requests through Manifest. In Manifest, configure a provider pointing to OpenRouter with a valid API key. Select a free-tier model, e.g. nvidia/nemotron-3-ultra-550b-a55b:free. Send a chat completion request via nanobot. Check the request details in Manifest's dashboard — status shows Success (200) but tokens are all 0. The client (nanobot) receives an empty response with no error indication.