fix: improve step 2 email switch handling

tests/signup-entry-diagnostics.test.js

@@ -112,10 +112,18 @@ function getSignupEmailInput() {
   return null;
 }
 
+function getSignupPhoneInput() {
+  return null;
+}
+
 function getSignupPasswordInput() {
   return null;
 }
 
+function findSignupUseEmailTrigger() {
+  return null;
+}
+
 function getPageTextSnapshot() {
   return 'Welcome to ChatGPT. Try our latest models.';
 }