feat: add WASM-based DOT transaction parsing via @bitgo/wasm-dot

Adds explainDotTransaction() using @bitgo/wasm-dot for parsing DOT
transactions. Includes proxy deposit cost handling for batch
stake/unstake explanations, high-level intent test migration, and
wasm-dot bumped to ^1.5.0 for unsigned tx blake2b IDs.

Ticket: BTC-3062

Author: lcovar

modules/sdk-coin-dot/package.json

@@ -43,6 +43,7 @@
     "@bitgo/sdk-core": "^36.34.0",
     "@bitgo/sdk-lib-mpc": "^10.9.0",
     "@bitgo/statics": "^58.30.0",
+    "@bitgo/wasm-dot": "^1.5.0",
     "@polkadot/api": "14.1.1",
     "@polkadot/api-augment": "14.1.1",
     "@polkadot/keyring": "13.5.6",

modules/sdk-coin-dot/src/dot.ts

@@ -58,14 +58,6 @@ export interface TransactionPrebuild {
   transaction: Interface.TxData;
 }
 
-export interface ExplainTransactionOptions {
-  txPrebuild: TransactionPrebuild;
-  publicKey: string;
-  feeInfo: {
-    fee: string;
-  };
-}
-
 export interface VerifiedTransactionParameters {
   txHex: string;
   prv: string;

modules/sdk-coin-dot/src/lib/index.ts

@@ -16,4 +16,6 @@ export { TransactionBuilderFactory } from './transactionBuilderFactory';
 export { SingletonRegistry } from './singletonRegistry';
 export { NativeTransferBuilder } from './nativeTransferBuilder';
 export { RemoveProxyBuilder } from './proxyBuilder';
+export { explainDotTransaction } from './wasmParser';
+export type { ExplainDotTransactionParams, DotWasmExplanation, DotInput } from './wasmParser';
 export { Interface, Utils };

modules/sdk-coin-dot/src/lib/transaction.ts

@@ -38,6 +38,7 @@ import {
 } from './iface';
 import { getAddress, getDelegateAddress } from './iface_utils';
 import utils from './utils';
+import { toJsonFromWasm } from './wasmParser';
 import BigNumber from 'bignumber.js';
 import { Vec } from '@polkadot/types';
 import { PalletConstantMetadataV14 } from '@polkadot/types/interfaces';
@@ -161,6 +162,20 @@ export class Transaction extends BaseTransaction {
     if (!this._dotTransaction) {
       throw new InvalidTransactionError('Empty transaction');
     }
+
+    // WASM path for signed tdot transactions — validates WASM parsing against production.
+    // Only for signed txs because toBroadcastFormat() returns the signed extrinsic (parseable).
+    // Unsigned txs return a signing payload (different format), so they use the legacy path.
+    if (this._coinConfig.name === 'tdot' && this._signedTransaction) {
+      return toJsonFromWasm({
+        txHex: this._signedTransaction,
+        material: utils.getMaterial(this._coinConfig),
+        senderAddress: this._sender,
+        coinConfigName: this._coinConfig.name,
+        referenceBlock: this._dotTransaction.blockHash,
+        blockNumber: Number(this._dotTransaction.blockNumber),
+      });
+    }
     const decodedTx = decode(this._dotTransaction, {
       metadataRpc: this._dotTransaction.metadataRpc,
       registry: this._registry,