feat(sdk-coin-xrp): add AccountDelete

[dgm003]

Ticket: CSHLD-716

Summary

Adds support for the XRPL AccountDelete transaction type to the XRP SDK, enabling
full reserve withdrawal recovery via the Wallet Recovery Wizard.(PR: BitGo/wallet-recovery-wizard#709)

Problem

XRP accounts hold a base reserve (1.2 XRP on mainnet, 0.2 XRP on testnet) that
standard Payment recovery transactions cannot access. Users with compromised or
abandoned wallets were unable to recover this locked balance.

Solution

Implement the XRPL AccountDelete transaction type, which permanently deletes an
account and transfers its entire balance including the base reserve to a
destination address.

Changes

sdk-core

• enum.ts — Added TransactionType.AccountDelete = 65 to the shared transaction type enum

sdk-coin-xrp — Builder layer

• iface.ts — Added AccountDelete to XrpTransactionType enum, extended XrpTransaction
  union type, added reserveWithdrawal?: boolean to RecoveryOptions and TxData
• accountDeleteBuilder.ts (new) — Builder for AccountDelete transactions, handles
  destination address and optional destination tag
• transactionBuilderFactory.ts — Wired getAccountDeleteBuilder() and routing in from()
• transaction.ts — Added serialisation (toJson), explanation
  (explainAccountDeleteTransaction), input/output extraction, and type mapping for
  AccountDelete
• index.ts — Exported AccountDeleteBuilder

sdk-coin-xrp — Recovery layer

• xrp.ts — Added reserveWithdrawal branch in recover() with the following
  precondition checks before building the AccountDelete transaction:
  • No trustlines with non-zero balances
  • No owned objects other than SignerList
  • Account age: Sequence + 256 ≤ currentLedger
  • Destination account must exist on the ledger
    Supports all three recovery modes: fully signed (non-KRS), half-signed (KRS), and
    unsigned sweep.

Tests

• test/resources/xrp.ts — Added mock fixtures: accountlinesResponseEmpty,
  accountObjectsResponse, accountObjectsResponseBlocking,
  destAccountInfoResponse, destAccountInfoNotFound
• test/unit/transactionBuilder/accountDeleteBuilder.ts (new) — 6 unit tests
  covering build with/without destination tag, round-trip rebuild from raw, and
  error cases for missing sender/destination
• test/unit/xrp.ts — 5 new tests for the recover() AccountDelete path covering
  fully signed, unsigned sweep, and all 3 precondition failure cases

Testing

Verified end-to-end on XRPL testnet via Wallet Recovery Wizard — transaction
broadcast with tesSUCCESS, account deleted and full balance (including reserve)
transferred to destination.

[kisslove-dewangan]

lgtm, based on codeowners

[abhi-bitgo]

@claude