Bump langgraph-sdk from 0.3.14 to 0.3.15

Bumps [langgraph-sdk](https://github.com/langchain-ai/langgraph) from 0.3.14 to 0.3.15.
- [Release notes](https://github.com/langchain-ai/langgraph/releases)
- [Commits](langchain-ai/langgraph@0.3.14...0.3.15)

---
updated-dependencies:
- dependency-name: langgraph-sdk
  dependency-version: 0.3.15
  dependency-type: direct:production
...

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

Author: dependabot[bot]

pyproject.toml

@@ -47,7 +47,7 @@ dependencies = [
 	"langchain-protocol==0.0.15",
 	"langgraph-checkpoint==4.1.0",
 	"langgraph-prebuilt==1.1.0",
-	"langgraph-sdk==0.3.14",
+	"langgraph-sdk==0.3.15",
 	"langgraph==1.2.0",
 	"langsmith==0.8.18",
 	"libipld==3.3.2",