feat: improved thinking/reasoning indicator with elapsed time counter

When the agent is reasoning with hidden thinking (thinking=low), show a
pulsing 'Reasoning...' indicator with elapsed time instead of generic
bouncing dots. Once text content starts streaming, falls back to the
regular streaming dots.

Closes feedback #40

src/components/ChatMessage.tsx

@@ -7,6 +7,7 @@ import remarkBreaks from 'remark-breaks';
 import rehypeHighlight from 'rehype-highlight';
 import type { ChatMessage as ChatMessageType, MessageBlock } from '../types';
 import { ThinkingBlock } from './ThinkingBlock';
+import { ThinkingIndicator } from './ThinkingIndicator';
 import { CodeBlock } from './CodeBlock';
 import { ToolCall } from './ToolCall';
 import { ImageBlock } from './ImageBlock';
@@ -388,14 +389,20 @@ export function ChatMessageComponent({ message, onRetry, agentAvatarUrl }: { mes
           {/* Inline images */}
           {renderImageBlocks(message.blocks)}
 
-          {/* Streaming dots */}
+          {/* Streaming indicator */}
-          {message.isStreaming && (
+          {message.isStreaming && (() => {
+            const hasVisibleContent = message.content?.trim();
+            if (!hasVisibleContent) {
+              return <ThinkingIndicator />;
+            }
+            return (
               <div className="flex gap-1 mt-2">
                 <span className="bounce-dot w-1.5 h-1.5 rounded-full bg-gradient-to-r from-cyan-300/80 to-violet-400/80 inline-block" />
                 <span className="bounce-dot w-1.5 h-1.5 rounded-full bg-gradient-to-r from-cyan-300/80 to-violet-400/80 inline-block" />
                 <span className="bounce-dot w-1.5 h-1.5 rounded-full bg-gradient-to-r from-cyan-300/80 to-violet-400/80 inline-block" />
               </div>
-          )}
+            );
+          })()}
 
           {/* Tool calls & thinking (inline) */}
           {!isUser && <InternalsSummary blocks={message.blocks} />}

src/components/ThinkingIndicator.tsx

@@ -0,0 +1,42 @@
+import { useState, useEffect, useRef } from 'react';
+import { Brain } from 'lucide-react';
+import { useT } from '../hooks/useLocale';
+
+/**
+ * Animated reasoning/thinking indicator shown during streaming
+ * when no text content has appeared yet (thinking=low mode).
+ * Displays elapsed time and a pulsing animation.
+ */
+export function ThinkingIndicator() {
+  const t = useT();
+  const [elapsed, setElapsed] = useState(0);
+  const startRef = useRef(Date.now());
+
+  useEffect(() => {
+    const interval = setInterval(() => {
+      setElapsed(Math.floor((Date.now() - startRef.current) / 1000));
+    }, 1000);
+    return () => clearInterval(interval);
+  }, []);
+
+  const formatElapsed = (s: number) => {
+    if (s < 60) return `${s}s`;
+    const m = Math.floor(s / 60);
+    const rem = s % 60;
+    return `${m}m ${rem.toString().padStart(2, '0')}s`;
+  };
+
+  return (
+    <div className="flex items-center gap-2 mt-2 animate-fade-in">
+      <div className="inline-flex items-center gap-2 rounded-2xl border border-violet-500/15 bg-violet-500/5 px-3 py-1.5">
+        <Brain size={14} className="text-violet-300 animate-pulse" />
+        <span className="text-xs font-medium text-violet-300">
+          {t('thinking.reasoning')}
+        </span>
+        <span className="text-xs tabular-nums text-violet-300/50">
+          {formatElapsed(elapsed)}
+        </span>
+      </div>
+    </div>
+  );
+}

src/lib/i18n.ts

@@ -60,6 +60,7 @@ const en = {
 
   // Thinking
   'thinking.label': 'Thinking',
+  'thinking.reasoning': 'Reasoning…',
 
   // Tool call
   'tool.parameters': 'Parameters',
@@ -151,6 +152,7 @@ const fr: Record<keyof typeof en, string> = {
   'sidebar.deleteCancel': 'Annuler',
 
   'thinking.label': 'Réflexion',
+  'thinking.reasoning': 'Réflexion…',
 
   'tool.parameters': 'Paramètres',
   'tool.result': 'Résultat',