core: docstrings shouldn't inherit from parents

> ```python > from langchain_core.tools import tool > from pydantic import BaseModel > > > class MyTool(BaseModel): > """Parent Tool""" > foo: str > > @tool > class ChildTool(MyTool): > bar: str > ``` > > For 0.4 release we could consider updating the behavior so that doc-strings are not inherited from their parents. It's fairly odd that doc-strings are inherited for BaseModels as in general the descriptions need to be different _Originally posted by @eyurtsev in [#31606](https://github.com/langchain-ai/langchain/issues/31606#issuecomment-3009548334)_