Markdown in user messages, with a preview in the composer

User messages are rendered with the same Markdown component as the model's
answers; single line breaks are kept (hard breaks outside code blocks), so
plain multi-line messages look as before. The eye button next to the text
field shows the formatted message before sending. The text sent to the model
is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/components/ChatView.tsx

@@ -608,9 +608,10 @@ function UserText({ text }: { text: string }) {
     const last = rest.pop()!;
     if (last.trim().endsWith(":")) break;
   }
+  const body = rest.join("\n").trim();
   return (
     <>
-      {rest.join("\n").trimEnd()}
+      {body && <Markdown text={body} breaks />}
       {files.length > 0 && (
         <div className="user-files">
           {files.map((f) => (