fix(checkpoint): widen Store put value type to Mapping[str, Any] (#8617)

TypedDict values don't structurally satisfy dict[str, Any] since dict
implies full mutability. Mapping[str, Any] accepts both plain dicts and
TypedDicts while still requiring string keys, matching what put()
actually needs from callers.

Fixes #8616

Verified by running lint/type/test locally across checkpoint,
checkpoint-sqlite, checkpoint-postgres, prebuilt, sdk-py, and a scoped
langgraph subset.

LinkedIn: https://linkedin.com/in/lisandro-navarra

---------

Co-authored-by: Mason Daugherty <github@mdrxy.com>

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

@@ -7,7 +7,7 @@ import logging
 import re
 import threading
 from collections import defaultdict
-from collections.abc import Callable, Iterable, Iterator, Sequence
+from collections.abc import Callable, Iterable, Iterator, Mapping, Sequence
 from contextlib import contextmanager
 from datetime import datetime
 from typing import (
@@ -354,7 +354,7 @@ class BasePostgresStore(Generic[C]):
                     (
                         _namespace_to_text(op.namespace),
                         op.key,
-                        Jsonb(cast(dict, op.value)),
+                        Jsonb(dict(cast(Mapping[str, Any], op.value))),
                     )
                 )
                 if op.ttl is not None: