refactor(shared/api): lazify queryClient to remove eager-construction footgun

queryClient.ts constructed the TanStack client at module eval but was not
in the sideEffects allowlist, so Rollup treated the module as pure — safe
only while a value-importer keeps it alive (D-3).

- replace the eager `queryClient` singleton with a memoized getQueryClient()
  factory; construction is deferred to first call
- the module is now genuinely side-effect-free, so no sideEffects exception
  is needed and construction can never be legally tree-shaken away
- route all consumers through getQueryClient() (QueryProvider as first
  caller; stores via class fields/observers; tests via a local alias; the
  fontCatalogStore spec mock now overrides getQueryClient)

src/shared/api/queryClient.ts

@@ -27,11 +27,16 @@ export const QUERY_RETRY_BASE_DELAY_MS = 1000;
  */
 export const QUERY_RETRY_MAX_DELAY_MS = 30000;
 
+let queryClientInstance: QueryClient | undefined;
+
 /**
- * TanStack Query client instance
+ * Shared TanStack Query client (lazy singleton).
  *
- * Configured for optimal caching and refetching behavior.
- * Used by all font stores for data fetching and caching.
+ * Construction is deferred to the first call so importing this module is inert:
+ * module eval runs no `new QueryClient()`, so the module is genuinely
+ * side-effect-free and needs no `sideEffects` allowlist exception. The
+ * app-layer `QueryProvider` is the first caller; every store reuses the same
+ * instance. Matches the lazy-accessor pattern used by the font stores.
  *
  * Cache behavior:
  * - Data stays fresh for 5 minutes (staleTime)
@@ -39,30 +44,32 @@ export const QUERY_RETRY_MAX_DELAY_MS = 30000;
  * - No refetch on window focus (reduces unnecessary network requests)
  * - 3 retries with exponential backoff on failure
  */
-export const queryClient = new QueryClient({
-    defaultOptions: {
-        queries: {
-            staleTime: DEFAULT_QUERY_STALE_TIME_MS,
-            gcTime: DEFAULT_QUERY_GC_TIME_MS,
-            /**
-             * Don't refetch when window regains focus
-             */
-            refetchOnWindowFocus: false,
-            /**
-             * Refetch on mount if data is stale
-             */
-            refetchOnMount: true,
-            retry: (failureCount, error) => {
-                if (error instanceof NonRetryableError) {
-                    return false;
-                }
-                return failureCount < QUERY_RETRY_COUNT;
+export function getQueryClient(): QueryClient {
+    return (queryClientInstance ??= new QueryClient({
+        defaultOptions: {
+            queries: {
+                staleTime: DEFAULT_QUERY_STALE_TIME_MS,
+                gcTime: DEFAULT_QUERY_GC_TIME_MS,
+                /**
+                 * Don't refetch when window regains focus
+                 */
+                refetchOnWindowFocus: false,
+                /**
+                 * Refetch on mount if data is stale
+                 */
+                refetchOnMount: true,
+                retry: (failureCount, error) => {
+                    if (error instanceof NonRetryableError) {
+                        return false;
+                    }
+                    return failureCount < QUERY_RETRY_COUNT;
+                },
+                /**
+                 * Exponential backoff: 1s, 2s, 4s, 8s... capped at 30s
+                 */
+                retryDelay: attemptIndex =>
+                    Math.min(QUERY_RETRY_BASE_DELAY_MS * 2 ** attemptIndex, QUERY_RETRY_MAX_DELAY_MS),
             },
-            /**
-             * Exponential backoff: 1s, 2s, 4s, 8s... capped at 30s
-             */
-            retryDelay: attemptIndex =>
-                Math.min(QUERY_RETRY_BASE_DELAY_MS * 2 ** attemptIndex, QUERY_RETRY_MAX_DELAY_MS),
         },
-    },
-});
+    }));
+}

src/shared/lib/helpers/BaseQueryStore/BaseQueryStore.svelte.ts

@@ -1,4 +1,4 @@
-import { queryClient } from '$shared/api/queryClient';
+import { getQueryClient } from '$shared/api/queryClient';
 import {
     QueryObserver,
     type QueryObserverOptions,
@@ -20,7 +20,7 @@ export abstract class BaseQueryStore<TData, TError = Error> {
     #unsubscribe: () => void;
 
     constructor(options: QueryObserverOptions<TData, TError, TData, any, any>) {
-        this.#observer = new QueryObserver(queryClient, options);
+        this.#observer = new QueryObserver(getQueryClient(), options);
         this.#unsubscribe = this.#observer.subscribe(result => {
             this.#result = result;
         });

src/shared/lib/helpers/BaseQueryStore/BaseQueryStore.test.ts

@@ -1,4 +1,6 @@
-import { queryClient } from '$shared/api/queryClient';
+import { getQueryClient } from '$shared/api/queryClient';
+
+const queryClient = getQueryClient();
 import {
     beforeEach,
     describe,