[shahin-hq]

Summary

Closes: https://app.clickup.com/t/2570579/86e2fc2w4

• Migrate transaction envelope to RLP (Mainsail/EVM-compatible) - replace the legacy Ark v2 binary format with [nonce, gasPrice, gasLimit, to, value, data, v, r, s] RLP encoding
• Add hand-rolled RLP codec (rlp.go) - typed RlpBytes/RlpBigInt/RlpList encode/decode, no external dependency
• Add ABI codec (abi.go, contracts.go) - function-call encode/decode for the 11 known Mainsail contract signatures
• Replace Schnorr signing with recoverable ECDSA (secp256k1)
• Rework network configuration - chainId-based Network
• New Transaction struct - EVM-shaped fields (Nonce/GasPrice/GasLimit/To/Value/Data/V/R/S/...) replacing the old asset-based model
• Rewrite serializer/deserializer around the RLP envelope + EIP-155 v encoding
• Rewrite transaction signing/verification - Sign, RecoverSender, Verify, GetHash, SigningHash
• Harden ABI/RLP decoders against malformed input - bounded integer conversions, list-length validation, no more silent truncation or panics on bad wire data
• Trim dependencies - drop btcsuite/btcd and ellemouton/schnorr entirely; move to decred/dcrd/dcrec/secp256k1/v4 directly; upgrade golang.org/x/crypto, testify
• Remove dead legacy-model code - enums.go, TransactionAsset/multisig types, and tests tied to the removed Schnorr/multisig builders
• Add end-to-end round-trip tests - sign → serialize → deserialize → verify, plus negative/edge cases

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[ItsANameToo]

can you add an implementation to https://github.com/ArdentHQ/sdk-tester-scripts to see it in action @shahin-hq ? that will make testing easier too

[shahin-hq]

@ItsANameToo

can you add an implementation to https://github.com/ArdentHQ/sdk-tester-scripts to see it in action @shahin-hq ? that will make testing easier too

Would you mind if I do that after having this one merged, because I'll implement tx builders in the next PR which will enable us testing?