[jsonschema] Fix RefResolver store parameter type (#15542)

Change URIDict to use MutableMapping[str, Any] as the value type
throughout, consistent with the actual runtime behavior where store
values are schema documents (JSON objects), not plain strings.

stubs/jsonschema/jsonschema/_utils.pyi

@@ -1,15 +1,20 @@
-from _typeshed import Incomplete, SupportsKeysAndGetItem, SupportsNext, SupportsRichComparison
+from _typeshed import Incomplete, SupportsNext, SupportsRichComparison
 from collections.abc import Generator, Iterable, Iterator, Mapping, MutableMapping
-from typing import Literal, TypeVar, overload
+from typing import Any, Literal, TypeVar, overload
 
 _T = TypeVar("_T")
 
-class URIDict(MutableMapping[str, str]):
+class URIDict(MutableMapping[str, MutableMapping[str, Any]]):
     def normalize(self, uri: str) -> str: ...
-    store: dict[str, str]
-    def __init__(self, m: SupportsKeysAndGetItem[str, str] | Iterable[tuple[str, str]], /, **kwargs: str) -> None: ...
-    def __getitem__(self, uri: str) -> str: ...
-    def __setitem__(self, uri: str, value: str) -> None: ...
+    store: dict[str, MutableMapping[str, Any]]
+    def __init__(
+        self,
+        m: Mapping[str, MutableMapping[str, Any]] | Iterable[tuple[str, MutableMapping[str, Any]]],
+        /,
+        **kwargs: MutableMapping[str, Any],
+    ) -> None: ...
+    def __getitem__(self, uri: str) -> MutableMapping[str, Any]: ...
+    def __setitem__(self, uri: str, value: MutableMapping[str, Any]) -> None: ...
     def __delitem__(self, uri: str) -> None: ...
     def __iter__(self) -> Iterator[str]: ...
     def __len__(self) -> int: ...

stubs/jsonschema/jsonschema/validators.pyi

@@ -113,7 +113,7 @@ class RefResolver:
         self,
         base_uri: str,
         referrer: dict[str, Incomplete],
-        store: SupportsKeysAndGetItem[str, str] | Iterable[tuple[str, str]] = ...,
+        store: Mapping[str, Mapping[str, Any]] | Iterable[tuple[str, Mapping[str, Any]]] = ...,
         cache_remote: bool = True,
         handlers: SupportsKeysAndGetItem[str, _Handler] | Iterable[tuple[str, _Handler]] = (),
         urljoin_cache=None,