feat(useragent): vibe-coded access list

useragent/lib/features/connection/evm/wallet_access.dart

@@ -0,0 +1,58 @@
+import 'package:arbiter/features/connection/connection.dart';
+import 'package:arbiter/proto/user_agent.pb.dart';
+import 'package:protobuf/well_known_types/google/protobuf/empty.pb.dart';
+
+Future<Set<int>> readClientWalletAccess(
+  Connection connection, {
+  required int clientId,
+}) async {
+  final response = await connection.ask(
+    UserAgentRequest(listWalletAccess: Empty()),
+  );
+  if (!response.hasListWalletAccessResponse()) {
+    throw Exception(
+      'Expected list wallet access response, got ${response.whichPayload()}',
+    );
+  }
+  return {
+    for (final access in response.listWalletAccessResponse.accesses)
+      if (access.clientId == clientId) access.walletId,
+  };
+}
+
+Future<void> writeClientWalletAccess(
+  Connection connection, {
+  required int clientId,
+  required Set<int> walletIds,
+}) async {
+  final current = await readClientWalletAccess(connection, clientId: clientId);
+
+  final toGrant = walletIds.difference(current);
+  final toRevoke = current.difference(walletIds);
+
+  if (toGrant.isNotEmpty) {
+    await connection.tell(
+      UserAgentRequest(
+        grantWalletAccess: SdkClientGrantWalletAccess(
+          accesses: [
+            for (final walletId in toGrant)
+              SdkClientWalletAccess(clientId: clientId, walletId: walletId),
+          ],
+        ),
+      ),
+    );
+  }
+
+  if (toRevoke.isNotEmpty) {
+    await connection.tell(
+      UserAgentRequest(
+        revokeWalletAccess: SdkClientRevokeWalletAccess(
+          accesses: [
+            for (final walletId in toRevoke)
+              SdkClientWalletAccess(clientId: clientId, walletId: walletId),
+          ],
+        ),
+      ),
+    );
+  }
+}