fix(chat): keep chatInstance getter on the widget (#7296)

Spreading the connector widget copied the getter's value (undefined before init), so widget.chatInstance was always undefined. Forward to the getter lazily instead.

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>

Author: Haroenv

packages/instantsearch.js/src/widgets/chat/__tests__/chat.test.tsx

@@ -22,6 +22,29 @@ describe('chat', () => {
     warning.cache = {};
   });
 
+  describe('chatInstance', () => {
+    test('is exposed on the widget once it has been initialized', async () => {
+      const container = document.createElement('div');
+      document.body.appendChild(container);
+
+      const search = instantsearch({
+        indexName: 'indexName',
+        searchClient: createSearchClient(),
+      });
+
+      const widget = chat({ container, agentId: 'test-agent-id' });
+
+      expect(widget.chatInstance).toBeUndefined();
+
+      search.addWidgets([widget]);
+      search.start();
+      await wait(0);
+
+      expect(widget.chatInstance).toBeDefined();
+      expect(widget.chatInstance.messages).toEqual([]);
+    });
+  });
+
   describe('options', () => {
     test('throws without a `container`', () => {
       expect(() => {

packages/instantsearch.js/src/widgets/chat/chat.tsx

@@ -1349,14 +1349,21 @@ export default (function chat<
     render(null, containerNode)
   );
 
+  const widget = makeWidget({
+    resume,
+    tools,
+    disableTriggerValidation: effectiveDisableTriggerValidation,
+    ...options,
+  });
+
   return {
-    ...makeWidget({
-      resume,
-      tools,
-      disableTriggerValidation: effectiveDisableTriggerValidation,
-      ...options,
-    }),
+    ...widget,
     $$widgetType: 'ais.chat',
+    // Spreading would copy the getter's value (still `undefined` before `init`),
+    // so we forward to it lazily instead.
+    get chatInstance() {
+      return widget.chatInstance;
+    },
   };
 } satisfies ChatWidget);