test: guard server cron mock args

src/gateway/server-cron.test.ts

@@ -126,8 +126,13 @@ function callArg(
   label: string,
 ) {
   const call = mock.mock.calls.at(callIndex);
-  expect(call, label).toBeDefined();
-  return call?.[argIndex];
+  if (!call) {
+    throw new Error(`Expected mock call: ${label}`);
+  }
+  if (argIndex >= call.length) {
+    throw new Error(`Expected mock call argument ${argIndex}: ${label}`);
+  }
+  return call[argIndex];
 }
 
 function expectHookContext(callIndex: number, fields: { config?: unknown; hasGetCron?: boolean }) {