fix: feedback buttons always visible, thread title update for untitled threads

- Remove opacity-0 group-hover from ThumbsUp/ThumbsDown buttons — always visible
- Fix thread title: update title whenever currentTitle is empty, not just first message

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

langgraph/src/main.tsx

@@ -153,7 +153,7 @@ function FeedbackButtons({ messageId }: { messageId: string }) {
           "inline-flex items-center text-xs px-1.5 py-0.5 rounded transition-colors",
           feedback === "up"
             ? "text-green-600 bg-green-100 dark:bg-green-900/30"
-            : "opacity-0 group-hover:opacity-100 text-muted-foreground hover:text-foreground hover:bg-accent",
+            : "text-muted-foreground hover:text-foreground hover:bg-accent",
         )}
         title="有帮助"
       >
@@ -166,7 +166,7 @@ function FeedbackButtons({ messageId }: { messageId: string }) {
           "inline-flex items-center text-xs px-1.5 py-0.5 rounded transition-colors",
           feedback === "down"
             ? "text-red-600 bg-red-100 dark:bg-red-900/30"
-            : "opacity-0 group-hover:opacity-100 text-muted-foreground hover:text-foreground hover:bg-accent",
+            : "text-muted-foreground hover:text-foreground hover:bg-accent",
         )}
         title="无帮助"
       >
@@ -588,8 +588,10 @@ function App() {
       },
     );
 
-    if (isFirstMessage && currentThreadId) {
-      // Smart title: truncate at word/punctuation boundary instead of mid-word
+    // Always set title if thread doesn't have one yet
+    if (currentThreadId && text) {
+      const currentTitle = threads.find((t) => t.thread_id === currentThreadId)?.metadata?.title;
+      if (!currentTitle || activeMessages.length === 0) {
         const rawTitle = text.slice(0, 30);
         const boundaryMatch = rawTitle.match(/^(.{10,}?)[，。！？、；：\s,.!?;:]/);
         const titleText = boundaryMatch ? boundaryMatch[1] : rawTitle.replace(/\s+\S*$/, "") || rawTitle;
@@ -604,6 +606,7 @@ function App() {
         );
       }
     }
+  }
 
   // ── Regenerate last AI message ───────────────────────────────────────────
   function handleRegenerate() {