Issue: Deprecation warning guides users to langchain.agents, breaking stream_mode="messages" token streaming

### 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 - [ ] langchain-openai - [ ] langchain-anthropic - [ ] langchain-classic - [x] langchain-core - [ ] langchain-cli - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [x] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-perplexity - [ ] langchain-prompty - [ ] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Example Code (Python) ```python import os from langchain_groq import ChatGroq from langchain_core.tools import tool # The "Working" Import from langgraph.prebuilt import create_react_agent as create_react_agent_graph # The "Broken" Import (Recommended by deprecation warning) from langchain.agents import create_react_agent as create_react_agent_legacy from langchain import hub # Setup if "GROQ_API_KEY" not in os.environ: os.environ["GROQ_API_KEY"] = "gsk_..." # User should insert key llm = ChatGroq(model="llama3-8b-8192", temperature=0, streaming=True) @tool def multiply(a: int, b: int) -> int: """Multiply two numbers.""" return a * b tools = [multiply] query = "What is 5 * 5?" print("--- 1. Testing LangGraph Agent (Should Stream) ---") graph_agent = create_react_agent_graph(llm, tools) for chunk, _ in graph_agent…