refactor: Use default centralized Flash & Pro models everywhere (#994)

packages/core/index.ts

@@ -5,3 +5,8 @@
  */
 
 export * from './src/index.js';
+export {
+  DEFAULT_GEMINI_MODEL,
+  DEFAULT_GEMINI_FLASH_MODEL,
+  DEFAULT_GEMINI_EMBEDDING_MODEL,
+} from './src/config/models.js';