feat: 统一智能体路由 + 删除 onboarding

- 新增 Unified 智能体（合并 health/diet/medication/exercise/default 全部工具）
- AI 自动判断意图并调用对应工具，前端胶囊自动切换
- 删除 onboarding 智能体及所有建档引导 UI
- 前端始终发 unified 类型，通过 tool_result 事件同步胶囊状态

health_app/lib/pages/home/widgets/chat_messages_view.dart

@@ -69,8 +69,6 @@ class ChatMessagesView extends ConsumerWidget {
         return _buildDietAnalysisCard(context, msg);
       case MessageType.reportAnalysis:
         return _buildReportAnalysisCard(context, msg);
-      case MessageType.onboarding:
-        return _buildOnboardingCard(context, ref);
       case MessageType.quickOptions:
         return _buildQuickOptionsCard(context, msg);
       default:
@@ -749,66 +747,7 @@ class ChatMessagesView extends ConsumerWidget {
     );
   }
 
-  // ═══════════════════════════════════════════════════════════
-  // 6. OnboardingCard — 首次建档引导
-  Widget _buildOnboardingCard(BuildContext context, WidgetRef ref) {
-    return Align(
-      alignment: Alignment.centerLeft,
-      child: Container(
-        margin: const EdgeInsets.only(bottom: 12),
-        constraints: BoxConstraints(maxWidth: MediaQuery.of(context).size.width * 0.88),
-        decoration: BoxDecoration(
-          color: Colors.white,
-          borderRadius: BorderRadius.circular(20),
-          boxShadow: [BoxShadow(color: const Color(0xFF8B9CF7).withAlpha(25), blurRadius: 14, offset: const Offset(0, 4))],
-        ),
-        clipBehavior: Clip.antiAlias,
-        child: Column(
-          mainAxisSize: MainAxisSize.min,
-          children: [
-            Container(
-              width: double.infinity,
-              padding: const EdgeInsets.fromLTRB(20, 24, 20, 16),
-              decoration: const BoxDecoration(
-                gradient: LinearGradient(colors: [Color(0xFF8B9CF7), Color(0xFFA78BFA)], begin: Alignment.topLeft, end: Alignment.bottomRight),
-              ),
-              child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
-                Row(children: [
-                  Container(width: 48, height: 48, decoration: BoxDecoration(color: Colors.white.withAlpha(30), borderRadius: BorderRadius.circular(14)), child: const Icon(Icons.health_and_safety, size: 28, color: Colors.white)),
-                  const SizedBox(width: 14),
-                  const Text('欢迎来到健康管家！', style: TextStyle(fontSize: 18, fontWeight: FontWeight.w700, color: Colors.white)),
-                ]),
-                const SizedBox(height: 12),
-                Text('我是您的AI健康管家。为了给您更精准的建议，\n我先了解一些基本信息好吗？大约2-3分钟。',
-                    style: TextStyle(fontSize: 14, color: Colors.white.withAlpha(220), height: 1.5)),
-              ]),
-            ),
-            Padding(
-              padding: const EdgeInsets.fromLTRB(18, 18, 18, 20),
-              child: Column(children: [
-                SizedBox(
-                  width: double.infinity,
-                  child: ElevatedButton(
-                    onPressed: () {
-                      ref.read(chatProvider.notifier).startOnboarding();
-                    },
-                    style: ElevatedButton.styleFrom(backgroundColor: const Color(0xFF8B9CF7), foregroundColor: Colors.white, shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(14)), padding: const EdgeInsets.symmetric(vertical: 14)),
-                    child: const Text('开始建档', style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600)),
-                  ),
-                ),
-                const SizedBox(height: 10),
-                TextButton(
-                    onPressed: () => ref.read(chatProvider.notifier).dismissOnboarding(),
-                    child: const Text('以后再说', style: TextStyle(fontSize: 14, color: Color(0xFF999999)))),
-              ]),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-
-  // 7. QuickOptionsCard — 优化样式
+  // 6. QuickOptionsCard — 优化样式
   // ═══════════════════════════════════════════════════════════
 
   Widget _buildQuickOptionsCard(BuildContext context, ChatMessage msg) {