fix(sdk-core): stamp enterprise-id header on getVaultConfig call

DefiVault.getVaultConfig() was calling the defi-service vault config
endpoint without the `enterprise-id` header that defi-service requires.
This caused the entire deposit flow to fail for UI clients whose access
tokens don't have `accessToken.enterprise` populated as a fallback in
WP's auth resolution.

Fix: call `.set('enterprise-id', this.wallet.toJSON().enterprise)` on
the GET request. The enterprise id is sourced directly from the wallet
context via the IWallet.toJSON() accessor — no constructor change needed,
consistent with how the wallet already owns its own data.

Tests: add `enterprise: 'test-enterprise-id'` to mock wallet data,
add `set: sinon.stub().returnsThis()` to mockRequest helper, and assert
`.set('enterprise-id', 'test-enterprise-id')` is called on the GET.

Ticket: DEFI-496
Session-Id: 1434552b-96ce-4eac-9922-cc2288aa5054
Task-Id: ba541f90-9eb1-45ed-a30f-a0605abde178

Author: venkateshv1266

modules/sdk-core/src/bitgo/defi/defiVault.ts

@@ -49,12 +49,10 @@ export class ActiveOperationExistsError extends Error {
 export class DefiVault implements IDefiVault {
   private readonly wallet: IWallet;
   private readonly bitgo: BitGoBase;
-  private readonly _enterpriseId: string;
 
-  constructor(wallet: IWallet, enterpriseId: string) {
+  constructor(wallet: IWallet) {
     this.wallet = wallet;
     this.bitgo = wallet.bitgo;
-    this._enterpriseId = enterpriseId;
   }
 
   /**
@@ -67,7 +65,7 @@ export class DefiVault implements IDefiVault {
     }
     const raw = await this.bitgo
       .get(this.bitgo.microservicesUrl(`/api/defi-service/v1/vaults/${params.vaultId}`))
-      .set('enterprise-id', this._enterpriseId)
+      .set('enterprise-id', this.wallet.toJSON().enterprise)
       .result();
     return decodeWithCodec(GetVaultResponse, raw, 'getVaultConfig');
   }

modules/sdk-core/src/bitgo/wallet/wallet.ts

@@ -3301,7 +3301,7 @@ export class Wallet implements IWallet {
    */
   get defi(): DefiVault {
     if (!this._defi) {
-      this._defi = new DefiVault(this, this._wallet.enterprise);
+      this._defi = new DefiVault(this);
     }
     return this._defi;
   }