fix(evm-wallet-experiment): update callVatExpectError to return error message directly

With the queueMessage RPC fix in @MetaMask/ocap-kernel, vat rejections now
surface as response.error with the actual message rather than a generic
'Internal error'. Update callVatExpectError in both the docker e2e helper
and the integration test runner to return response.error.message directly
and throw on unexpected success, replacing the dead response.result.body path.

Author: grypez

packages/evm-wallet-experiment/test/e2e/docker/helpers/daemon-client.mjs

@@ -46,10 +46,10 @@ async function callVat(socketPath, target, method, args = []) {
 async function callVatExpectError(socketPath, target, method, args = []) {
   const response = await rpc(socketPath, 'queueMessage', [target, method, args]);
   if (response.error) {
-    return JSON.stringify(response.error);
+    return response.error.message;
   }
   await waitUntilQuiescent();
-  return response.result.body;
+  throw new Error(`Expected error but call succeeded: ${JSON.stringify(response.result)}`);
 }
 
 /**

packages/evm-wallet-experiment/test/integration/run-daemon-wallet.mjs

@@ -125,7 +125,8 @@ async function callVat(socketPath, target, method, args = []) {
 }
 
 /**
- * Send a queueMessage RPC expecting it to return an error CapData.
+ * Send a queueMessage RPC expecting it to fail, and return the error message.
+ * Throws if the call unexpectedly succeeds.
  *
  * @param {string} socketPath
  * @param {string} target
@@ -140,12 +141,12 @@ async function callVatExpectError(socketPath, target, method, args = []) {
     args,
   ]);
   if (response.error) {
-    // RPC-level error (method dispatch failed)
-    return JSON.stringify(response.error);
+    return response.error.message;
   }
-  // Vat-level error (method threw, encoded as CapData)
   await waitUntilQuiescent();
-  return response.result.body;
+  throw new Error(
+    `Expected error but call succeeded: ${JSON.stringify(response.result)}`,
+  );
 }
 
 // ---------------------------------------------------------------------------
@@ -315,10 +316,7 @@ async function main() {
     'signMessage',
     ['should fail'],
   );
-  assert(
-    errorBody.includes('#error') || errorBody.includes('No authority'),
-    'error surfaces through daemon',
-  );
+  assert(errorBody.includes('No authority'), 'error surfaces through daemon');
 
   // -----------------------------------------------------------------------
   // Test 10: Terminate subcluster via daemon