fix: expose SDK instance for plugin API access via singleton

- Make ExperienceRuntime.sdk public (not readonly) for Proxy access
- Add default export for IIFE build to expose singleton correctly
- Update singleton Proxy to dynamically access defaultInstance.sdk
- Remove manual window assignment (handled by IIFE build)
- Fixes playground integration where experiences.modal was undefined

This enables script tag users to access plugin APIs via global:
experiences.modal.show(), experiences.inline.show(), etc.

Author: prosdev

packages/core/src/index.ts

@@ -15,19 +15,22 @@ export {
   evaluateExperience,
   evaluateUrlRule,
 } from './runtime';
-
 // Export singleton API
+// Default export for IIFE builds (script tag)
+// This is what gets exposed as window.experiences
 export {
   createInstance,
   destroy,
   evaluate,
   evaluateAll,
+  experiences, // Named exportexperiences as default,
   explain,
   getState,
   init,
   on,
   register,
 } from './singleton';
+
 // Export all types
 export type {
   BannerContent,

packages/core/src/runtime.ts

@@ -33,7 +33,7 @@ import type {
  * - Explainability-first (every decision has reasons)
  */
 export class ExperienceRuntime {
-  private sdk: SDK;
+  public sdk: SDK; // Public for plugin API access via Proxy (readonly would prevent reinit)
   private experiences: Map<string, Experience> = new Map();
   private decisions: Decision[] = [];
   private initialized = false;

packages/core/src/singleton.ts

@@ -177,8 +177,10 @@ export async function destroy(): Promise<void> {
  * import experiences from '@prosdevlab/experience-sdk';
  * await experiences.init();
  * ```
+ *
+ * For IIFE builds (script tag), this becomes window.experiences via default export
  */
-export const experiences = {
+const experiencesObject = {
   createInstance,
   init,
   register,
@@ -188,23 +190,17 @@ 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;
-  },
 };
 
-/**
- * Global singleton instance for IIFE builds
- *
- * When loaded via script tag, this object is available as `window.experiences`
- */
-if (typeof window !== 'undefined') {
-  (window as unknown as Record<string, unknown>).experiences = experiences;
-}
+const experiencesProxy = new Proxy(experiencesObject, {
+  get(target, prop) {
+    // Check wrapper functions first
+    if (prop in target && target[prop as keyof typeof target]) {
+      return target[prop as keyof typeof target];
+    }
+    // Fall back to SDK instance for plugin APIs (modal, inline, banner, etc.)
+    return (defaultInstance.sdk as any)[prop];
+  },
+});
+
+export { experiencesProxy as experiences };