chore(docs): update x handle references (#37081)

## Description
Updates package metadata and README badges so LangChain social links
point to the new `@langchain_oss` X handle. This was completed with
AI-agent assistance.

## Test Plan
- [ ] Validate README badges and package metadata links point to
`https://x.com/langchain_oss`

_Opened collaboratively by Mason Daugherty and open-swe._

---------

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
Co-authored-by: Mason Daugherty <61371264+mdrxy@users.noreply.github.com>

libs/partners/openrouter/README.md

@@ -3,7 +3,7 @@
 [![PyPI - Version](https://img.shields.io/pypi/v/langchain-openrouter?label=%20)](https://pypi.org/project/langchain-openrouter/#history)
 [![PyPI - License](https://img.shields.io/pypi/l/langchain-openrouter)](https://opensource.org/licenses/MIT)
 [![PyPI - Downloads](https://img.shields.io/pepy/dt/langchain-openrouter)](https://pypistats.org/packages/langchain-openrouter)
-[![Twitter](https://img.shields.io/twitter/url/https/twitter.com/langchain.svg?style=social&label=Follow%20%40LangChain)](https://x.com/langchain)
+[![Twitter](https://img.shields.io/twitter/url/https/twitter.com/langchain_oss.svg?style=social&label=Follow%20%40LangChain)](https://x.com/langchain_oss)
 
 ## Quick Install
 

libs/partners/openrouter/pyproject.toml

@@ -33,7 +33,7 @@ Documentation = "https://reference.langchain.com/python/integrations/langchain_o
 Repository = "https://github.com/langchain-ai/langchain"
 Issues = "https://github.com/langchain-ai/langchain/issues"
 Changelog = "https://github.com/langchain-ai/langchain/releases?q=%22langchain-openrouter%22"
-Twitter = "https://x.com/LangChain"
+Twitter = "https://x.com/langchain_oss"
 Slack = "https://www.langchain.com/join-community"
 Reddit = "https://www.reddit.com/r/LangChain/"