[API sync] Handle sweep_tx event and swept_vtxos from GetTransactionsStream (arkd#988)

[arkanaai]

Context

arkd#988 (Forward sweep txs event in transaction stream) was merged to master at 2026-03-23T09:16:57Z.

What changed in arkd

Two additive changes to the GetTransactionsStream gRPC + REST API:

1. New sweep_tx event type on GetTransactionsStreamResponse (field 4)

message GetTransactionsStreamResponse {
  oneof data {
    TxNotification commitment_tx = 1;
    TxNotification ark_tx = 2;
    Heartbeat heartbeat = 3;
    TxNotification sweep_tx = 4;  // NEW
  }
}

2. New swept_vtxos field on TxNotification (field 6)

message TxNotification {
  ...
  repeated Outpoint swept_vtxos = 6;  // NEW
}

3. OpenAPI / REST — both service.openapi.json and types.openapi.json updated

Required updates in this SDK

• Regenerate ark-grpc bindings from updated proto (sweep_tx variant, SweptVtxos field)
• Regenerate ark-rest OpenAPI client (sweepTx + sweptVtxos)
• Handle SweepTx variant in GetTransactionsStream stream dispatcher in ark-grpc/src/client.rs
• Expose swept_vtxos on TxNotification Rust type
• Update get_transactions_stream_response.rs and related model files
• Add tests

Reference

• arkd PR: Transaction stream: add sweep tx event arkd#988
• Commit: eeb0baef6937b7544e0f659edbeee58f8aa2a90e

/cc @luckysori @philipp