RuntimeError in _AsyncHttpxClientWrapper.__del__ when event loop is closed

### Checked other resources - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] This is not related to the langchain-community package. - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Package (Required) - [x] langchain - [x] langchain-openai - [x] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-openrouter - [ ] langchain-perplexity - [ ] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Related Issues / PRs _No response_ ### Reproduction Steps / Example Code (Python) ```python import asyncio import gc from langchain_openai.chat_models._client_utils import _AsyncHttpxClientWrapper async def main(): client = _AsyncHttpxClientWrapper(base_url="http://test", timeout=10) # used... pass if __name__ == "__main__": asyncio.run(main()) # Logic: loop is closed here gc.collect() # Trigger __del__ -> RuntimeError: no running event loop ``` ### Error Message and Stack Trace (if applicable) ```shell ``` ### Description Description: I found a resource cleanup issue in langchain-openai and langchain-anthropic. The `_AsyncHttpxClientWrapper.__del__` method attempts to schedule an async cleanup task using `asyncio.get_running_loop()`. However, if the object is garbage collected during interpreter shutdown or in a co…