fix(account-lib): update module imports for Node 22 ESM compatibility

Modified sinon stubbing approach to work with ESM modules by using
require() and monkey patching instead of direct imports, which allows
tests to function correctly after migrating from ts-node to tsx.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

TICKET: WP-5599

Author: zahin-mohammad

modules/account-lib/test/unit/mpc/tss/ecdsa/ecdsa.ts

@@ -4,10 +4,9 @@
 import assert from 'assert';
 import { Hash, randomBytes } from 'crypto';
 import { Ecdsa, ECDSA, hexToBigInt } from '@bitgo/sdk-core';
-import { EcdsaPaillierProof, EcdsaTypes, Schnorr, SchnorrProof } from '@bitgo/sdk-lib-mpc';
+import { EcdsaPaillierProof, EcdsaTypes, SchnorrProof } from '@bitgo/sdk-lib-mpc';
 import * as sinon from 'sinon';
 import createKeccakHash from 'keccak';
-import * as paillierBigint from 'paillier-bigint';
 import {
   schnorrProofs,
   ntildes,
@@ -19,6 +18,12 @@ import {
   mockFKeyShare,
 } from '../fixtures/ecdsa';
 
+// Need to import and then monkey-patch to make stubbing work with ESM
+const paillierBigintModule = require('paillier-bigint');
+const paillierBigint = paillierBigintModule;
+const schnorrModule = require('@bitgo/sdk-lib-mpc');
+const Schnorr = schnorrModule.Schnorr;
+
 describe('TSS ECDSA TESTS', function () {
   const MPC = new Ecdsa();
   const base = BigInt('0x010000000000000000000000000000000000000000000000000000000000000000'); // 2^256
@@ -30,23 +35,35 @@ describe('TSS ECDSA TESTS', function () {
   );
   let A: ECDSA.KeyShare, B: ECDSA.KeyShare, C: ECDSA.KeyShare;
   before(async () => {
-    const paillierMock = sinon
-      .stub(paillierBigint, 'generateRandomKeys')
+    // Direct monkey patching of the module for ESM compatibility
+    const originalGenerateRandomKeys = paillierBigint.generateRandomKeys;
+
+    const paillierMock = sinon.stub();
+    paillierMock
       .onCall(0)
-      .resolves(paillerKeys[0] as unknown as paillierBigint.KeyPair)
+      .resolves(paillerKeys[0])
       .onCall(1)
-      .resolves(paillerKeys[1] as unknown as paillierBigint.KeyPair)
+      .resolves(paillerKeys[1])
       .onCall(2)
-      .resolves(paillerKeys[2] as unknown as paillierBigint.KeyPair)
+      .resolves(paillerKeys[2])
       .onCall(3)
-      .resolves(paillerKeys[0] as unknown as paillierBigint.KeyPair)
+      .resolves(paillerKeys[0])
       .onCall(4)
-      .resolves(paillerKeys[1] as unknown as paillierBigint.KeyPair)
+      .resolves(paillerKeys[1])
       .onCall(5)
-      .resolves(paillerKeys[2] as unknown as paillierBigint.KeyPair);
+      .resolves(paillerKeys[2]);
+
+    // Replace the function directly on the module
+    paillierBigint.generateRandomKeys = paillierMock;
+
+    // Save references to restore later
+    (paillierMock as any).originalFn = originalGenerateRandomKeys;
 
-    const schnorrProofMock = sinon
-      .stub(Schnorr, 'createSchnorrProof')
+    // Apply the same monkey-patching approach for Schnorr
+    const originalCreateSchnorrProof = Schnorr.createSchnorrProof;
+
+    const schnorrProofMock = sinon.stub();
+    schnorrProofMock
       .onCall(0)
       .returns(schnorrProofs[0] as unknown as SchnorrProof)
       .onCall(1)
@@ -60,6 +77,12 @@ describe('TSS ECDSA TESTS', function () {
       .onCall(5)
       .returns(schnorrProofs[5] as unknown as SchnorrProof);
 
+    // Replace the function directly on the module
+    Schnorr.createSchnorrProof = schnorrProofMock;
+
+    // Save references to restore later
+    (schnorrProofMock as any).originalFn = originalCreateSchnorrProof;
+
     [A, B, C] = await Promise.all([MPC.keyShare(1, 2, 3), MPC.keyShare(2, 2, 3), MPC.keyShare(3, 2, 3)]);
 
     // Needs to run this serially for testing deterministic key generation
@@ -96,10 +119,13 @@ describe('TSS ECDSA TESTS', function () {
       hKeyCombine,
     ];
     commonPublicKey = aKeyCombine.xShare.y;
-    paillierMock.reset();
-    paillierMock.restore();
-    schnorrProofMock.reset();
-    schnorrProofMock.restore();
+    // Adding an explicit assertion to check if the stub was used
+    paillierMock.callCount.should.equal(6, 'paillierMock should be called 6 times');
+    schnorrProofMock.callCount.should.equal(8, 'schnorrProofMock should be called 6 times');
+
+    // Restore original functions
+    paillierBigint.generateRandomKeys = (paillierMock as any).originalFn;
+    Schnorr.createSchnorrProof = (schnorrProofMock as any).originalFn;
   });
 
   describe('Ecdsa Key Generation Test', function () {
@@ -149,10 +175,7 @@ describe('TSS ECDSA TESTS', function () {
     });
 
     it('should pass if seed length is greater than 64', async function () {
-      const paillierMock = sinon
-        .stub(paillierBigint, 'generateRandomKeys')
-        .onCall(0)
-        .resolves(paillerKeys[0] as unknown as paillierBigint.KeyPair);
+      const paillierMock = sinon.stub(paillierBigint, 'generateRandomKeys').onCall(0).resolves(paillerKeys[0]);
       const seed72Bytes = Buffer.from(
         '4f7e914dc9ec696398675d1544aab61cb7a67662ffcbdb4079ec5d682be565d87c1b2de75c943dec14c96586984860268779498e6732473aed9ed9c2538f50bea0af926bdccc0134',
         'hex',