Fix returning annotator training skip

frontend/src/pages/GuidelinePage.jsx

@@ -1,4 +1,3 @@
-
 import React, { useEffect, useState } from "react";
 import GuidelineContent from "./GuidelineContent";
 
@@ -11,12 +10,6 @@ export default function GuidelinePage({
   onLookupResult
 }) {
   const nameIsValid = annotatorName.trim().length > 0;
-
-  // Lightweight name-collision guard: there's no login, so two different
-  // people could type the same name and accidentally share an assignment.
-  // This is advisory only (a self-reported checkbox), not proof of identity
-  // - see GET /assignment/lookup, which never creates anything, just reports
-  // whether a name is already in use.
   const [collisionInfo, setCollisionInfo] = useState(null);
   const [collisionAcknowledged, setCollisionAcknowledged] = useState(false);
 
@@ -24,27 +17,31 @@ export default function GuidelinePage({
     setCollisionAcknowledged(false);
 
     const name = annotatorName.trim();
-    if (!name || !apiBaseUrl) {
+    if (!name) {
       setCollisionInfo(null);
+      onLookupResult?.({ exists: false });
       return undefined;
     }
 
     let cancelled = false;
     const timer = setTimeout(() => {
-      fetch(`${apiBaseUrl}/assignment/lookup?annotator=${encodeURIComponent(name)}`)
+      // In production apiBaseUrl is intentionally an empty string because
+      // the frontend and backend share the same origin. An empty base URL
+      // must therefore still perform the lookup using the relative route.
+      fetch(`${apiBaseUrl || ""}/assignment/lookup?annotator=${encodeURIComponent(name)}`)
         .then((res) => (res.ok ? res.json() : { exists: false }))
         .then((data) => {
           if (cancelled) return;
           setCollisionInfo(data.exists ? data : null);
-          // A round only ever exists for a name that already passed
-          // training (see App.jsx's handleGuidelineLookupResult) - reuse
-          // this same lookup instead of firing a second request just to
-          // check that.
           onLookupResult?.(data);
         })
         .catch(() => {
-          // Fail open - this check is advisory, never block name entry on a lookup error.
-          if (!cancelled) setCollisionInfo(null);
+          // Fail open: the collision check is advisory and should not block
+          // a new annotator if the lookup endpoint is temporarily unavailable.
+          if (!cancelled) {
+            setCollisionInfo(null);
+            onLookupResult?.({ exists: false });
+          }
         });
     }, 400);