xlm: Soroban SAC token transfers to contract addresses

[cordialsys-agent]

Summary

• Migrate Stellar SDK from stellar/go to stellar/go-stellar-sdk v0.4.0 (adds Soroban support)
• Add support for token transfers to Soroban contract (C...) addresses via Stellar Asset Contract (SAC) invocation
• When destination is a C address, the driver builds an InvokeHostFunction operation calling the SAC transfer(from, to, amount) function
• Soroban simulation via secondary_url (Soroban RPC) provides resource fees and authorization entries

How it works

1. FetchTransferInput detects C-address destination, builds a temporary tx, simulates via Soroban RPC
2. Simulation results (SorobanData, auth entries, resource fee) are stored in TxInput
3. Builder constructs InvokeHostFunction operation with the SAC contract derived from the token asset
4. Transaction includes SorobanTransactionData extension and combined fee (inclusion + resource)

Config

Requires secondary_url in chain config pointing to Soroban RPC:

XLM:
  url: "https://horizon-testnet.stellar.org"
  secondary_url: "https://soroban-testnet.stellar.org"

Test plan

Tested live on Stellar testnet with YLDS token:

• Normal YLDS transfer (Payment op) — 532306e0
• YLDS transfer with fee-payer — 359f4552
• YLDS to contract C address (SAC InvokeHostFunction) — d405ff77
• YLDS to contract C address with fee-payer — c896e377

Also verified no regressions on mainnet:

• Normal XLM transfer — 98bdd85c
• USDC token transfer — 2a381808
• XLM with fee-payer — 66893adb

🤖 Generated with Claude Code

[conorpp]

  ┌─────┬─────────┬─────────────────────────────┬──────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
  │  #  │ Network │            Test             │   Hash   │                                                   Explorer                                                    │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 1   │ Testnet │ YLDS transfer               │ 5b6de503 │ https://testnet.stellarchain.io/transactions/5b6de50305598129f646e5960ae7cb7401801b89f9ca4cdf78dbb99ce4748e59 │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 2   │ Testnet │ YLDS + fee-payer            │ 05e6a56f │ https://testnet.stellarchain.io/transactions/05e6a56fa735c217ded63b3a6db3dc03ef3e7c1a7144f56388478ff7874eb7a3 │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 3   │ Testnet │ YLDS → contract C addr      │ 06f12e11 │ https://testnet.stellarchain.io/transactions/06f12e11c0c75af18a8c904cadc5fed51ad6b3c39cea4c4702cd0873496a6a00 │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 4   │ Testnet │ YLDS → contract + fee-payer │ cab663c3 │ https://testnet.stellarchain.io/transactions/cab663c3e0935c19a4fc4ed63b8cfa020706bb7038373836cb67dd5f6a29227b │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 5   │ Testnet │ XLM transfer                │ 59db75c7 │ https://testnet.stellarchain.io/transactions/59db75c73c771047481f659067b6cc17b87f00eb30b98c781a334b5e49725903 │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 6   │ Testnet │ XLM + fee-payer             │ 00957c36 │ https://testnet.stellarchain.io/transactions/00957c36f4f5692321477f0c2e1fda2aa7632860e922109f955e2a979797e81a │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 7   │ Mainnet │ XLM transfer                │ 1660a21f │ https://stellarchain.io/transactions/1660a21fbd43d91fc6aff74a9f505a5d423d7b648073088f2e24871b40849f61         │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 8   │ Mainnet │ XLM + fee-payer             │ 6dc76f50 │ https://stellarchain.io/transactions/6dc76f506f3a1ab2748941b53f185a724930e981992678d23b20e38b2f40a53f         │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 9   │ Mainnet │ USDC transfer               │ 3950cdb2 │ https://stellarchain.io/transactions/3950cdb2ae1b1c8f71da35e48d69daec415990f8483ff8979b1228327e3f1570         │
  ├─────┼─────────┼─────────────────────────────┼──────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ 10  │ Mainnet │ USDC + fee-payer            │ b5528e95 │ https://stellarchain.io/transactions/b5528e952a4956ce70a9ef10e24eeb7555419b58f8c14f5e2f825fb290f2684b         │
  └─────┴─────────┴─────────────────────────────┴──────────┴───────────────────────────────────────────────────────────────────────────────────────────────────────────────┘