Add ability to steer an agent in the create_agent flow

### Checked other resources - [x] This is a feature request, not a bug report or usage question. - [x] I added a clear and descriptive title that summarizes the feature request. - [x] I used the GitHub search to find a similar feature request and didn't find it. - [x] I checked the LangChain documentation and API reference to see if this feature already exists. - [x] This is not related to the langchain-community package. ### Package (Required) - [ ] langchain - [ ] langchain-openai - [ ] 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 ### Feature Description The ability to steer an agent mid multi-turn execution is becoming prevalent in leading multi-turn tools (claude code, GH copilot) Could this be something that is considered in the `create_aegnt` wrapper? ### Use Case Suited to all longer time horizon use cases ### Proposed Solution - perhaps some form of method "push steer" that queues steer requests, and injects them as "user" messages into the context state graph in between turns? - I appreciate this might be complex and need async / thread management! ### Alternatives Considered _No response_ ### Additional Context _No response_