enhance(ai-help): add model to issue reports (#10925)

* enhance(ai-help): add model to issue reports

* fix(ai-help): add "(None)" for answers without source

As `[].join("\n")` is never `null`, this wasn't working so far.

client/src/plus/ai-help/index.tsx

@@ -1083,6 +1083,9 @@ function ReportIssueOnGitHubLink({
   currentMessage: Message;
   children: React.ReactNode;
 }) {
+  const user = useUserData();
+  const isSubscriber = useMemo(() => isPlusSubscriber(user), [user]);
+
   const gleanClick = useGleanClick();
   const currentMessageIndex = messages.indexOf(currentMessage);
   const questions = messages
@@ -1105,8 +1108,10 @@ function ReportIssueOnGitHubLink({
         (source) =>
           `- [${source.title}](https://developer.mozilla.org${source.url})`
       )
-      .join("\n") ?? "(None)"
+      .join("\n") || "(None)"
   );
+  // TODO Persist model in messages and read it from there.
+  sp.set("model", isSubscriber ? "gpt-4" : "gpt-3.5");
   sp.set("template", "ai-help-answer.yml");
 
   url.search = sp.toString();