Fix unused imports in user preferences service contract

- Remove unused FavoritesValue and RecentItemsValue imports from contracts
- Update doc comment to use FavoriteEntry[] instead of FavoritesValue
- Keep imports minimal to avoid linting errors

Agent-Logs-Url: https://github.com/objectstack-ai/framework/sessions/b54b7f1e-4c8c-42f9-9546-3efcd7c0dbf7

Co-authored-by: xuyushun441-sys <255036401+xuyushun441-sys@users.noreply.github.com>

Author: Claude

packages/spec/src/contracts/user-preferences-service.ts

@@ -1,6 +1,6 @@
 // Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
 
-import type { UserPreferenceEntry, FavoriteEntry, FavoritesValue, RecentItemsValue } from '../identity/user-preference.zod';
+import type { UserPreferenceEntry, FavoriteEntry } from '../identity/user-preference.zod';
 
 /**
  * IUserPreferencesService — User Preferences Service Contract
@@ -24,7 +24,7 @@ import type { UserPreferenceEntry, FavoriteEntry, FavoritesValue, RecentItemsVal
  * await prefs.set('user123', 'theme', 'light');
  *
  * // Get structured data (favorites)
- * const favorites = await prefs.get<FavoritesValue>('user123', 'favorites');
+ * const favorites = await prefs.get<FavoriteEntry[]>('user123', 'favorites');
  *
  * // Set multiple preferences at once
  * await prefs.setMany('user123', {