fix(core): expose plugin APIs through singleton

- Add getter properties for modal, inline, banner on singleton
- Allows script tag users to access window.experiences.modal.show()
- Fixes playground getting stuck at 'Loading Experience SDK...'

Now window.experiences.modal, .inline, .banner are available

Author: prosdev

packages/core/src/singleton.ts

@@ -188,6 +188,16 @@ export const experiences = {
   getState,
   on,
   destroy,
+  // Expose plugin APIs from the default instance
+  get modal() {
+    return (defaultInstance as any).modal;
+  },
+  get inline() {
+    return (defaultInstance as any).inline;
+  },
+  get banner() {
+    return (defaultInstance as any).banner;
+  },
 };
 
 /**