fix(checkpoint-postgres): type blob_values as Sequence[tuple[bytes, bytes, bytes]]

Replace Any with the concrete element type — each row is (key, type_tag,
blob) all as bytes — matching how _load_blobs unpacks and decodes them.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

libs/checkpoint-postgres/langgraph/checkpoint/postgres/base.py

@@ -248,7 +248,7 @@ class BasePostgresSaver(BaseCheckpointSaver[str]):
 
     def _load_blobs(
         self,
-        blob_values: Any,
+        blob_values: Sequence[tuple[bytes, bytes, bytes]],
     ) -> dict[str, Any]:
         if not blob_values:
             return {}