fix: resolve typecheck errors in databinding-advanced harness tests

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people

example/__tests__/databinding-advanced.harness.ts

@@ -1,5 +1,8 @@
 import { describe, it, expect } from 'react-native-harness';
-import type { ViewModelInstance } from '@rive-app/react-native';
+import type {
+  ViewModelInstance,
+  ViewModelStringProperty,
+} from '@rive-app/react-native';
 import { RiveFileFactory } from '@rive-app/react-native';
 
 const DATABINDING = require('../assets/rive/databinding.riv');
@@ -15,15 +18,6 @@ async function loadFile(source: number) {
   return RiveFileFactory.fromSource(source, undefined);
 }
 
-async function createGordonInstance(): Promise<ViewModelInstance> {
-  const file = await loadFile(DATABINDING);
-  const vm = file.viewModelByName('Person');
-  expectDefined(vm);
-  const instance = vm.createInstanceByName('Gordon');
-  expectDefined(instance);
-  return instance;
-}
-
 describe('RiveFile ViewModel Access', () => {
   it('viewModelCount returns expected count', async () => {
     const file = await loadFile(DATABINDING);
@@ -136,7 +130,7 @@ describe('ViewModel Creation Variants', () => {
     expectDefined(vm);
 
     // Legacy returns undefined, experimental returns an empty instance
-    const instance = vm.createInstanceByIndex(100);
+    vm.createInstanceByIndex(100);
     expect(true).toBe(true);
   });
 
@@ -195,9 +189,9 @@ describe('List Properties', () => {
 
     const names = ['Gordon', 'David', 'Tod', 'Erik', 'Adam'];
     for (let i = 0; i < names.length; i++) {
-      const item = list.getInstanceAt(i);
+      const item: ViewModelInstance = list.getInstanceAt(i)!;
       expectDefined(item);
-      const nameProp = item.stringProperty('name');
+      const nameProp: ViewModelStringProperty = item.stringProperty('name')!;
       expectDefined(nameProp);
       expect(nameProp.value).toBe(names[i]);
     }