Warn when passing in block types not supported by a model

See [comment](https://github.com/langchain-ai/langchain/issues/33395#issuecomment-3387475515) Certain models don't support modalities like audio input (e.g. `gpt-4o`). If we see an incoming audio block (e.g. `AudioContentBlock`) in the content, we may eventually wish to warn the user.