fix(ux): improve interaction feedback and fix pre-tool text rendering

- Show pre-tool plainTextContent above ToolCallStatus (was silently
  dropped when hasThinking=false but plainText exists with tool_calls)
- Pre-tool thinking bubble gets proper bg-muted bubble styling and
  isStreaming=false (thinking is complete once tool calls start)
- handleRegenerate now sets concurrentStatus="generating" for
  consistent status bar feedback on regenerate
- Remove dead setConcurrentStatus prop from ChatInput interface/usage

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

langgraph/src/components/ChatInput.tsx

@@ -15,7 +15,6 @@ interface ChatInputProps {
   sourceLabel: string | null;
   setSourceLabel: (v: string | null) => void;
   concurrentStatus: "idle" | "generating" | "stopping" | "cancelling";
-  setConcurrentStatus: (s: "idle" | "generating" | "stopping" | "cancelling") => void;
   onSubmit: (e: React.FormEvent) => void;
   onStop: () => void;
   onPaste: (e: React.ClipboardEvent) => void;

langgraph/src/components/ChatMessages.tsx

@@ -305,9 +305,9 @@ export function ChatMessages({
 
           return (
             <div key={message.id ?? idx} className="flex flex-col gap-3">
-              {hasThinking && hasToolCalls && (
-                <div className="max-w-[85%]">
-                  <MessageBubble content={bubbleContent} role="ai" isStreaming={thread.isLoading && isLastAi} />
+              {hasToolCalls && (plainTextContent || hasThinking) && (
+                <div className="max-w-[85%] rounded-2xl rounded-bl-sm bg-muted text-foreground px-4 py-2.5 text-sm">
+                  <MessageBubble content={bubbleContent} role="ai" isStreaming={false} />
                 </div>
               )}
 

langgraph/src/main.tsx

@@ -275,6 +275,7 @@ function App() {
     const lastHuman = humanMsgs[humanMsgs.length - 1];
     if (!lastHuman || thread.isLoading) return;
 
+    setConcurrentStatus("generating");
     const enabledTools =
       activeTools.size > 0
         ? TOOL_GROUPS.filter((g) => activeTools.has(g.key)).flatMap((g) => [...g.tools])
@@ -450,7 +451,6 @@ function App() {
             sourceLabel={sourceLabel}
             setSourceLabel={setSourceLabel}
             concurrentStatus={concurrentStatus}
-            setConcurrentStatus={setConcurrentStatus}
             onSubmit={handleSubmit}
             onStop={handleStop}
             onPaste={handlePaste}