fix(web): stop sign-in with an email code from landing back on /signin

packages/web/src/pages/sign-in-page/ConfirmEmailPage.tsx

@@ -51,10 +51,14 @@ export const ConfirmEmailPage = () => {
       const sanitizedOtp = otp.replace(/\s/g, '')
       dispatch(setValueField('otp', sanitizedOtp))
       dispatch(setValueField('email', email))
-      dispatch(startSignUp())
+      // Only guests finish sign-up from here. For everyone else this would
+      // open the sign-up welcome modal after a plain sign-in.
+      if (isGuest) {
+        dispatch(startSignUp())
+      }
       dispatch(signIn(email, password, sanitizedOtp))
     },
-    [dispatch, email, password]
+    [dispatch, email, password, isGuest]
   )
 
   return (

packages/web/src/pages/sign-on-page/SignOnPage.tsx

@@ -1,4 +1,4 @@
-import { ReactNode, useEffect, useLayoutEffect } from 'react'
+import { ReactNode, useEffect, useLayoutEffect, useRef } from 'react'
 
 import { SystemAppearance } from '@audius/common/models'
 import { FEED_PAGE } from '@audius/common/src/utils/route'
@@ -318,7 +318,16 @@ export const SignOnPage = () => {
   const location = useLocation()
   const isSignUp = location.pathname.startsWith(SIGN_UP_PAGE)
 
+  // The sign-on saga resets status to editing right after success, often
+  // before the navigation to the completion route commits (it suspends on
+  // lazy pages). Rendering the form again would remount the sign-in routes,
+  // and their first-mount redirect to /signin would cancel that navigation.
+  const hasSucceededRef = useRef(false)
   if (signOnStatus === EditingStatus.SUCCESS) {
+    hasSucceededRef.current = true
+  }
+
+  if (hasSucceededRef.current) {
     return <Navigate to={completionRoute || FEED_PAGE} />
   }