fix: use better string conversion for message signing

It appears that `v instanceof Buffer` is not a reliable type guard in Typescript
5.

The new type guard is equivalent.

Issue: BTC-1450

Author: OttoAllmendinger

modules/abstract-eth/src/lib/transferBuilder.ts

@@ -155,8 +155,8 @@ export class TransferBuilder {
 
     if (this._coinUsesNonPackedEncodingForTxData) {
       const types: string[] = operationData[0] as string[];
-      const values: string[] = operationData[1].map((item) =>
-        item instanceof Buffer ? '0x' + item.toString('hex') : item
+      const values: (string | number)[] = operationData[1].map((item) =>
+        typeof item === 'string' || typeof item === 'number' ? item : '0x' + item.toString('hex')
       );
       operationHash = keccak256(defaultAbiCoder.encode(types, values));
     } else {
@@ -166,7 +166,7 @@ export class TransferBuilder {
     return operationHash;
   }
 
-  protected getOperationData(): (string | Buffer)[][] {
+  protected getOperationData(): (string | number | Buffer)[][] {
     let operationData;
     const prefix = this.getOperationHashPrefix();
     if (this._tokenContractAddress !== undefined) {

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

@@ -161,7 +161,7 @@ export class Ada extends BaseCoin {
   /** @inheritDoc */
   async signMessage(key: KeyPair, message: string | Buffer): Promise<Buffer> {
     const adaKeypair = new AdaKeyPair({ prv: key.prv });
-    const messageHex = message instanceof Buffer ? message.toString('hex') : message;
+    const messageHex = typeof message === 'string' ? message : message.toString('hex');
 
     return Buffer.from(adaKeypair.signMessage(messageHex));
   }

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

@@ -247,7 +247,7 @@ export class Cspr extends BaseCoin {
    */
   async signMessage(key: KeyPair, message: string | Buffer): Promise<Buffer> {
     const keyPair = new CsprLib.KeyPair({ prv: key.prv });
-    const messageHex = message instanceof Buffer ? message.toString('hex') : message;
+    const messageHex = typeof message === 'string' ? message : message.toString('hex');
     const signatureData = CsprLib.Utils.signMessage(keyPair, messageHex);
     return Buffer.from(signatureData.signature);
   }

modules/sdk-coin-polygon/test/unit/transactionBuilder/send.ts

@@ -23,7 +23,7 @@ describe('Polygon transaction builder send', () => {
       ];
       const types: string[] = operationParams[0] as string[];
       const values: (string | number)[] = operationParams[1].map((item) =>
-        item instanceof Buffer ? '0x' + item.toString('hex') : item
+        typeof item === 'string' || typeof item === 'number' ? item : '0x' + item.toString('hex')
       );
       return keccak256(defaultAbiCoder.encode(types, values));
     };