feat(useragent): vibe-coded access list

useragent/lib/providers/sdk_clients/details.dart

@@ -0,0 +1,19 @@
+import 'package:arbiter/proto/user_agent.pb.dart';
+import 'package:arbiter/providers/sdk_clients/list.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+part 'details.g.dart';
+
+@riverpod
+Future<SdkClientEntry?> clientDetails(Ref ref, int clientId) async {
+  final clients = await ref.watch(sdkClientsProvider.future);
+  if (clients == null) {
+    return null;
+  }
+  for (final client in clients) {
+    if (client.id == clientId) {
+      return client;
+    }
+  }
+  return null;
+}