fix(desktop): 隐藏Hand状态消息 + 过滤LLM工具调用叙述

1. 所有 role=hand 的消息不再显示 (不仅仅是 researcher)
   - "Hand: hand_researcher - running" 不再出现
   - Hand 错误 JSON 不再显示
   - 移除未使用的 PresentationContainer import

2. 添加 stripToolNarration() 过滤 LLM 推理文本
   - 英文: "Now let me...", "I need to...", "I keep getting..."
   - 中文: "让我执行...", "让我尝试使用...", "好的，让我为您..."
   - 保留实际有用内容，仅过滤工具调用叙述

验证: tsc --noEmit 零错误, vitest 343 pass (1 pre-existing fail)

desktop/src/components/ChatArea.tsx

@@ -34,7 +34,6 @@ import { ModelSelector } from './ai/ModelSelector';
 import { isTauriRuntime } from '../lib/tauri-gateway';
 import { SuggestionChips } from './ai/SuggestionChips';
 import { PipelineResultPreview } from './pipeline/PipelineResultPreview';
-import { PresentationContainer } from './presentation/PresentationContainer';
 // TokenMeter temporarily unused — using inline text counter instead
 
 // Default heights for virtualized messages
@@ -637,12 +636,36 @@ export function ChatArea({ compact, onOpenDetail }: { compact?: boolean; onOpenD
   );
 }
 
+/**
+ * Strip LLM tool-usage narration from response content.
+ * When the LLM calls tools (search, fetch, etc.), it often narrates its reasoning
+ * in English ("Now let me execute...", "I need to provide...", "I keep getting errors...")
+ * and Chinese ("让我执行...", "让我尝试..."). These are internal thoughts, not user-facing content.
+ */
+function stripToolNarration(content: string): string {
+  const sentences = content.split(/(?<=[。！？.!?])\s*/);
+  const filtered = sentences.filter(s => {
+    const t = s.trim();
+    if (!t) return false;
+    // English narration patterns
+    if (/^(?:Now )?[Ll]et me\s/i.test(t)) return false;
+    if (/^I\s+(?:need to|keep getting|should|will try|have to|can try|must)\s/i.test(t)) return false;
+    if (/^The hand_researcher\s/i.test(t)) return false;
+    // Chinese narration patterns
+    if (/^让我(?:执行|尝试|使用|进一步|调用|运行)/.test(t)) return false;
+    if (/^好的，让我为您/.test(t)) return false;
+    return true;
+  });
+  const result = filtered.join(' ').replace(/\s{2,}/g, ' ').trim();
+  return result || content; // Fallback: if everything was stripped, show original
+}
+
 function MessageBubble({ message, onRetry }: { message: Message; setInput?: (text: string) => void; onRetry?: () => void }) {
   if (message.role === 'tool') {
     return null;
   }
-  // Researcher hand results are internal — search results are already in the LLM reply
+  // Hand status/result messages are internal — search results are already in the LLM reply
-  if (message.role === 'hand' && message.handName === 'researcher') {
+  if (message.role === 'hand') {
     return null;
   }
 
@@ -721,15 +744,15 @@ function MessageBubble({ message, onRetry }: { message: Message; setInput?: (tex
                 ? (isUser
                     ? message.content
                     : <StreamingText
-                        content={message.content}
+                        content={stripToolNarration(message.content)}
                         isStreaming={!!message.streaming}
                         className="text-gray-700 dark:text-gray-200"
                       />
                   )
                 : '...'}
             </div>
-            {/* Pipeline / Hand result presentation */}
+            {/* Pipeline result presentation */}
-            {!isUser && (message.role === 'workflow' || message.role === 'hand') && message.workflowResult && typeof message.workflowResult === 'object' && message.workflowResult !== null && (
+            {!isUser && message.role === 'workflow' && message.workflowResult && typeof message.workflowResult === 'object' && message.workflowResult !== null && (
               <div className="mt-3">
                 <PipelineResultPreview
                   outputs={message.workflowResult as Record<string, unknown>}
@@ -737,11 +760,6 @@ function MessageBubble({ message, onRetry }: { message: Message; setInput?: (tex
                 />
               </div>
             )}
-            {!isUser && message.role === 'hand' && message.handResult && typeof message.handResult === 'object' && message.handResult !== null && !message.workflowResult && message.handName !== 'researcher' && (
-              <div className="mt-3">
-                <PresentationContainer data={message.handResult} />
-              </div>
-            )}
             {message.error && (
               <div className="flex items-center gap-2 mt-2">
                 <p className="text-xs text-red-500">{message.error}</p>