Sync indexer proto: GetVtxoChain/GetVirtualTxs auth fields (arkd#904)

[arkanaai]

Context

arkd#904 merged (aff0d89679) adding indexer exposure and auth to GetVtxoChain and GetVirtualTxs.

Proto changes in arkd

ark/v1/indexer.proto now has:

message IndexerIntent {
  string proof = 1;
  string message = 2;
}

message GetVtxoChainRequest {
  // ... existing fields ...
  oneof auth {
    IndexerIntent intent = 3;
    string token = 4;
  }
}

message GetVtxoChainResponse {
  // ... existing fields ...
  string auth_token = 3;
}

message GetVirtualTxsRequest {
  // ... existing fields ...
  oneof auth {
    IndexerIntent intent = 3;
    string token = 4;
  }
}

message GetVirtualTxsResponse {
  // ... existing fields ...
  string auth_token = 3;
}

What needs updating in dotnet-sdk

1. NArk.Core/Transport/GrpcClient/Protos/ark/v1/indexer.proto — sync from arkd
2. Regenerate gRPC stubs from updated proto
3. Update any REST client types if present

Behavioral notes

• Changes are additive — existing calls without auth fields still work (default exposure is public)
• When arkd is configured with INDEXER_EXPOSURE=withheld or INDEXER_EXPOSURE=private, callers must provide an intent or valid token
• Tokens from GetVtxoChain can be recycled for GetVirtualTxs and vice versa

Reference

• arkd PR: Require Intent for GetVtxoChain/GetVirtualTxs arkd#904
• Merged commit: arkade-os/arkd@aff0d89679

[from: cross-repo-impact agent, 2026-04-02]