feat(server): KB prompt优化、字幕修复、S2S重连、助手配置API

- assistantProfileConfig: KB answer prompt改为分层策略(严格产品信息+灵活常识补充)
- nativeVoiceGateway: S2S upstream自动重连(最多50次)、event 351字幕debounce(800ms取最长文本)
- toolExecutor: 确定性query改写增强、KB查询传递session上下文
- contextKeywordTracker: 支持KB话题记忆优先enrichment
- contentSafeGuard: 新增品牌安全内容过滤服务
- assistantProfileService: 新增助手配置CRUD服务
- routes/assistantProfile: 新增助手配置API路由
- knowledgeKeywords: 扩展KB关键词词典
- fastAsrCorrector: ASR纠错规则更新
- tests/: KB prompt测试、保护窗口测试、Viking性能测试
- docs/: 助手配置API文档、系统提示词目录

test2/server/services/nativeVoiceGateway.js

@@ -29,6 +29,7 @@ const {
   buildVoiceSystemRole,
   buildVoiceGreeting,
 } = require('./assistantProfileConfig');
+const { getAssistantProfile } = require('./assistantProfileService');
 
 const sessions = new Map();
 
@@ -498,6 +499,10 @@ async function processReply(session, text, turnSeq = session.latestUserTurnSeq |
           session._lastKbTopic = cleanText;
           session._lastKbHitAt = Date.now();
         }
+        // 直接用KB原始回答作为字幕，不依赖S2S event 351（S2S可能拆段/改写/丢失内容）
+        const ragSubtitleText = ragContent.map((item) => item.content).join(' ');
+        persistAssistantSpeech(session, ragSubtitleText, { source, toolName, meta: responseMeta });
+        session.lastDeliveredAssistantTurnSeq = activeTurnSeq;
         session._pendingExternalRagReply = true;
         await sendExternalRag(session, ragContent);
         session.awaitingUpstreamReply = true;
@@ -1003,7 +1008,10 @@ function attachClientHandlers(session) {
     }
 
     if (parsed.type === 'start') {
+      session.userId = parsed.userId || session.userId || null;
+      const remoteProfileResult = await getAssistantProfile({ userId: session.userId });
       const assistantProfile = resolveAssistantProfile({
+        ...(remoteProfileResult.profile || {}),
         ...(session.assistantProfile || {}),
         ...((parsed.assistantProfile && typeof parsed.assistantProfile === 'object') ? parsed.assistantProfile : {}),
       });
@@ -1014,7 +1022,6 @@ function attachClientHandlers(session) {
       session.speaker = parsed.speaker || process.env.VOLC_S2S_SPEAKER_ID || 'zh_female_vv_jupiter_bigtts';
       session.modelVersion = parsed.modelVersion || 'O';
       session.greetingText = parsed.greetingText || buildVoiceGreeting(assistantProfile);
-      session.userId = parsed.userId || session.userId || null;
       // 立即发送 ready，不等 upstream event 150，大幅缩短前端等待时间
       sendReady(session);
       session.upstream = createUpstreamConnection(session);