[Cross-Repo] Add max_op_return_outputs to GetInfo response type

[arkanaai]

Context

arkd PR #987 was merged (2026-03-19T14:55:44Z) adding max_op_return_outputs to the gRPC GetInfoResponse (proto field 21) and OpenAPI spec.

arkd change: api-spec/protobuf/ark/v1/service.proto

int64 max_op_return_outputs = 21;

OpenAPI: maxOpReturnOutputs added to GetInfoResponse schema.

What needs to change in dotnet-sdk

• Regenerate or update gRPC/protobuf bindings to include MaxOpReturnOutputs
• Expose the field in the SDK's Info model / GetInfoAsync() return type
• Optionally: use the value to enforce client-side OP_RETURN limits before submitting transactions

Impact

Without this, dotnet-sdk consumers cannot read the server's configured OP_RETURN limit and may construct transactions that get rejected by newer arkd versions.

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Opened by: Arkana cross-repo impact analyzer
Trigger: arkade-os/arkd@0a5e8d1a merged to master