fix(flutter/test): tolerate Riverpod 3's ProviderException wrapper

flutter_client/test/player/player_provider_test.dart

@@ -14,7 +14,19 @@ void main() {
   test('audioHandlerProvider must be overridden — bare read throws', () {
     final container = ProviderContainer();
     addTearDown(container.dispose);
-    expect(() => container.read(audioHandlerProvider), throwsA(isA<UnimplementedError>()));
+    // Riverpod 3 wraps the underlying error in a ProviderException. The
+    // intent of the test is "bare read fails," so accept the wrapper as
+    // long as the inner error is the UnimplementedError we threw.
+    expect(
+      () => container.read(audioHandlerProvider),
+      throwsA(predicate((e) {
+        if (e is UnimplementedError) return true;
+        // ProviderException is private to riverpod; match by name + by
+        // walking its toString for the inner UnimplementedError text.
+        return e.runtimeType.toString().contains('ProviderException') &&
+            e.toString().contains('UnimplementedError');
+      })),
+    );
   });
 
   test('overridden audioHandlerProvider exposes playbackState stream', () {