fix(wallet-sdk): use derived contract address in registerContract (#24482)

## Problem

CI on `merge-train/fairies-v5` is red at the `yarn-project` build step
([ci.aztec-labs.com/1783026321562696](http://ci.aztec-labs.com/1783026321562696)).
The `compile_all` → `yarn tsgo -b --emitDeclarationOnly` typecheck fails
with:

```
wallet-sdk/src/base-wallet/base_wallet.ts(375,36): error TS2339: Property 'address' does not exist on type 'ContractInstancePreimage'.
wallet-sdk/src/base-wallet/base_wallet.ts(377,113): error TS2339: Property 'address' does not exist on type 'ContractInstancePreimage'.
```

These two were the complete set of errors reported by the
(non-fail-fast) tsgo pass.

## Root cause

This is a train-integration break, not a defect in the commit the CI run
is attributed to (#24480, which only touched a TXE registry type). On
the `v5-next` base, `ContractInstancePreimage` was refactored to no
longer store a derived `address` field (address is now computed from the
preimage; the with-address variant is the separate
`ContractInstancePreimageWithAddress`). The fairies train's rewrite of
`BaseWallet.registerContract` still read `instance.address`, which no
longer exists on that type.

## Fix

`PXE.registerContract(instance)` already returns the derived
`AztecAddress` (it computes
`computeContractAddressFromInstance(instance)` internally). Capture and
use that returned address for the account-mismatch assertion instead of
the removed `instance.address` field. This is semantically identical —
the returned value is exactly the address the field used to hold — and
touches only the two failing references.

## Verification

The workspace this fix was prepared in is a bare checkout with no
build/test cache available (no redis/docker) and insufficient free disk
for a from-scratch `bb` + `noir` + TS build, so a full local
`./bootstrap.sh ci-fast` could not be run to completion. The change is
verified by inspection against the type definitions and the
`PXE.registerContract` return contract; CI on this PR will exercise the
real build.


---
*Created by
[claudebox](https://claudebox.work/v2/sessions/8542372f24dbb848) ·
group: `slackbot`*

Author: AztecBot

yarn-project/wallet-sdk/src/base-wallet/base_wallet.ts

@@ -358,7 +358,7 @@ export abstract class BaseWallet implements Wallet {
     if (artifact) {
       await this.pxe.registerContractClass(artifact);
     }
-    await this.pxe.registerContract(instance);
+    const contractAddress = await this.pxe.registerContract(instance);
 
     if (secretKeyOrKeys) {
       // PXE never receives the account seed (from which the message-signing/fallback secret keys could be re-derived):
@@ -372,9 +372,9 @@ export abstract class BaseWallet implements Wallet {
           ? await deriveKeys(secretKeyOrKeys)
           : await deriveKeysFromMasterSecretKeys(secretKeyOrKeys);
       const { address } = await this.pxe.registerAccount(derivedKeys, await computePartialAddress(instance));
-      if (!address.equals(instance.address)) {
+      if (!address.equals(contractAddress)) {
         throw new Error(
-          `Registered account address ${address.toString()} does not match contract instance address ${instance.address.toString()}: the provided keys do not correspond to this account.`,
+          `Registered account address ${address.toString()} does not match contract instance address ${contractAddress.toString()}: the provided keys do not correspond to this account.`,
         );
       }
     }