Non-dict tool arguments should be set invalid

### 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) - [ ] langchain - [x] 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 ### Related Issues / PRs _No response_ ### Reproduction Steps / Example Code (Python) ```python The `tool_call` field of AIMessage requires its arguments to be an dict: class ToolCall(TypedDict): """Represents an AI's request to call a tool. Example: {"name": "foo", "args": {"a": 1}, "id": "123"} This represents a request to call the tool named `'foo'` with arguments `{"a": 1}` and an identifier of `'123'`. !!! note "Factory function" `tool_call` may also be used as a factory to create a `ToolCall`. Benefits include: * Required arguments strictly validated at creation time """ name: str """The name of the tool to be called.""" args: dict[str, Any] """The arguments to the tool call as a dictionary.""" id: str | None """An identifier associate…