LLM Observability streamed tool-call TypeError fixed; OpenRouter cost tracking hardened

Bug Fixes

• LLM Observability: Resolves a TypeError raised during streamed tool-call reconstruction when an OpenAI-compatible backend (e.g. DashScope/Qwen) e mits a tool-call delta with function.arguments or custom.input set to None instead of "".

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• LLM Observability: Resolves an issue where the OpenAI and LiteLLM integrations reported zero cost for OpenRouter requests using a bring-your-own-ke y setup.