chore(deps): bump langgraph from 1.2.0 to 1.2.1

Bumps [langgraph](https://github.com/langchain-ai/langgraph) from 1.2.0 to 1.2.1.
- [Release notes](https://github.com/langchain-ai/langgraph/releases)
- [Commits](langchain-ai/langgraph@1.2.0...1.2.1)

---
updated-dependencies:
- dependency-name: langgraph
  dependency-version: 1.2.1
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]