fix: guard preferences save against uninitialized store

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/stores/preferences.svelte.ts

@@ -14,18 +14,29 @@ const DEFAULT_PREFERENCES: Preferences = {
 };
 
 let store: Store | null = null;
+let loadPromise: Promise<void> | null = null;
 
 export const preferences = $state<Preferences>({ ...DEFAULT_PREFERENCES });
 
 export async function loadPreferences(): Promise<void> {
+  if (loadPromise) {
+    await loadPromise;
+    return;
+  }
+  loadPromise = (async () => {
     store = await load('preferences.json', { autoSave: true });
     const savedDir = await store.get<string>('outputDirectory');
     const savedCookie = await store.get<CookieSource>('cookieSource');
     if (savedDir) preferences.outputDirectory = savedDir;
     if (savedCookie) preferences.cookieSource = savedCookie;
+  })();
+  await loadPromise;
 }
 
 export async function savePreferences(): Promise<void> {
+  if (!store) {
+    await loadPreferences();
+  }
   if (!store) return;
   await store.set('outputDirectory', preferences.outputDirectory);
   await store.set('cookieSource', preferences.cookieSource);