fix(svelte-query): don't wrap observers in derived to avoid state_unsafe_mutation

fixes useIsFetching and useIsMutating in svelte 5 adapter

Author: hmnd

packages/svelte-query/src/createBaseQuery.svelte.ts

@@ -39,11 +39,15 @@ export function createBaseQuery<
   })
 
   /** Creates the observer */
-  const observer = $derived(
-    new Observer<TQueryFnData, TError, TData, TQueryData, TQueryKey>(
-      client,
-      untrack(() => resolvedOptions),
-    ),
+  const observer = new Observer<
+    TQueryFnData,
+    TError,
+    TData,
+    TQueryData,
+    TQueryKey
+  >(
+    client,
+    untrack(() => resolvedOptions),
   )
 
   function createResult() {

packages/svelte-query/src/createMutation.svelte.ts

@@ -26,24 +26,23 @@ export function createMutation<
 ): CreateMutationResult<TData, TError, TVariables, TContext> {
   const client = useQueryClient(queryClient?.())
 
-  const observer = $derived(
-    new MutationObserver<TData, TError, TVariables, TContext>(
-      client,
-      options(),
-    ),
+  const observer = new MutationObserver<TData, TError, TVariables, TContext>(
+    client,
+    options(),
   )
 
-  const mutate = $state<
-    CreateMutateFunction<TData, TError, TVariables, TContext>
-  >((variables, mutateOptions) => {
+  const mutate = <CreateMutateFunction<TData, TError, TVariables, TContext>>((
+    variables,
+    mutateOptions,
+  ) => {
     observer.mutate(variables, mutateOptions).catch(noop)
   })
 
   $effect.pre(() => {
     observer.setOptions(options())
   })
 
-  const result = $state(observer.getCurrentResult())
+  const result = observer.getCurrentResult()
 
   const unsubscribe = observer.subscribe((val) => {
     notifyManager.batchCalls(() => {

packages/svelte-query/src/createQueries.svelte.ts

@@ -216,12 +216,10 @@ export function createQueries<
     }),
   )
 
-  const observer = $derived(
-    new QueriesObserver<TCombinedResult>(
-      client,
-      untrack(() => resolvedQueryOptions),
-      untrack(() => combine as QueriesObserverOptions<TCombinedResult>),
-    ),
+  const observer = new QueriesObserver<TCombinedResult>(
+    client,
+    untrack(() => resolvedQueryOptions),
+    untrack(() => combine as QueriesObserverOptions<TCombinedResult>),
   )
 
   function createResult() {