fix: add async setup() method to AsyncRedisSaver (#74)

Add async setup() method to AsyncRedisSaver that delegates to asetup()
to match the canonical pattern used by PostgreSQL and SQLite checkpointers.

This fixes the RuntimeWarning caused by calling the inherited sync setup()
method from BaseRedisSaver, which called async create() methods without
awaiting them.

Maintains backward compatibility by keeping the existing asetup() method
while providing the standard async setup() interface that users expect
from LangGraph checkpointers.

Fixes #74

Author: bsbodden

langgraph/checkpoint/redis/aio.py

@@ -152,6 +152,21 @@ async def asetup(self) -> None:
         # Detect cluster mode if not explicitly set
         await self._detect_cluster_mode()
 
+    async def setup(self) -> None:  # type: ignore[override]
+        """Set up the checkpoint saver asynchronously.
+
+        This method creates the necessary indices in Redis and detects cluster mode.
+        It MUST be called before using the checkpointer.
+
+        This async method follows the canonical pattern used by PostgreSQL and SQLite
+        checkpointers in the LangGraph ecosystem. The type ignore is necessary because
+        the base class defines a sync setup() method, but async checkpointers require
+        an async setup() method to properly handle coroutines.
+
+        Usage: await checkpointer.setup()
+        """
+        await self.asetup()
+
     async def _detect_cluster_mode(self) -> None:
         """Detect if the Redis client is a cluster client by inspecting its class."""
         if self.cluster_mode is not None: