feat: 全链路追踪系统 — ai-core追踪事件 + ethend管道视图

ai-core:
- 新增 TraceEvent 内存环形缓冲区(200条)
- GET /api/v1/trace/events 端点（支持session_id过滤）
- 预置 trace.go 追踪事件定义

ethend:
- trace/recent 聚合 platform-bridge消息日志 + ai-core追踪事件
- 消息按管线分组: msg_received→llm_call→tool_call→msg_sent
- 前端管线卡片视图: 每条消息显示完整处理步骤

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

ethend/src/index.js

@@ -1277,16 +1277,16 @@ function parseLogTimestamp(line) {
 app.get('/api/trace/recent', async (req, res) => {
   const limit = Math.min(parseInt(req.query.limit) || 50, 200);
   try {
-    const [llmResult, toolResult, sessionsResult, bridgeLogsResult, aiCoreLogsResult] = await Promise.all([
+    const [llmResult, toolResult, sessionsResult, bridgeLogsResult, traceEventsResult] = await Promise.all([
       proxyToAICore(`/api/v1/llm-calls?limit=${limit}`).catch(() => ({ status: 502, body: [] })),
       proxyToAICore(`/api/v1/tools/calls?limit=${limit}`).catch(() => ({ status: 502, body: { calls: [] } })),
       proxyToGateway('/api/v1/admin/sessions/active').catch(() => ({ status: 502, body: { users: {} } })),
       // 拉 platform-bridge 最近的消息日志
-      Promise.all((['obv11', 'qq']).map(platform =>
-        proxyToPlatformBridge(`/api/v1/logs/${platform}?limit=50`).catch(() => ({ status: 502, body: { entries: [] } }))
+      Promise.all((['obv11']).map(platform =>
+        proxyToPlatformBridge(`/api/v1/logs/${platform}?limit=50`).catch(() => ({ status: 502, body: { logs: [] } }))
       )),
-      // 拉 ai-core 最近的日志（解析处理事件）
-      proxyToAICore('/api/v1/llm-calls/stream?limit=0').catch(() => ({ status: 502, body: [] })),
+      // 拉 ai-core 追踪事件
+      proxyToAICore(`/api/v1/trace/events?limit=${limit}`).catch(() => ({ status: 502, body: { events: [] } })),
     ]);
 
     const traces = [];
@@ -1349,6 +1349,23 @@ app.get('/api/trace/recent', async (req, res) => {
       });
     }
 
+    // === ai-core 追踪事件 (intent, subsession, synthesis, etc.) ===
+    const traceEvents = traceEventsResult.body?.events || [];
+    for (const ev of traceEvents) {
+      const ts = ev.timestamp ? new Date(ev.timestamp).getTime() : Date.now();
+      traces.push({
+        id: ev.id || `trace-${ts}`,
+        timestamp: new Date(ts).toISOString(), ts,
+        service: 'ai-core',
+        hop: ev.hop || 'trace',
+        label: ev.label || '',
+        status: ev.status || 'success',
+        durationMs: ev.duration_ms || 0,
+        detail: ev.detail || '',
+        data: ev.data || {},
+      });
+    }
+
     // === 活跃会话 ===
     const users = sessionsResult.body?.users || {};
     for (const [userID, sessions] of Object.entries(users)) {