优化实时聊天：稳定 WS、按 seq 增量同步，并修复访客评价推送

- 客服/访客 WebSocket 不再因切换会话反复重连，断线自动恢复
- 新增 after_seq 增量拉取，重连与消息空洞时 catch-up
- 结束会话同时推送给访客，预览页可弹出评价并支持兜底状态同步

server/internal/handler/session.go

@@ -2,6 +2,7 @@ package handler
 
 import (
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 	"unicode/utf8"
@@ -145,9 +146,12 @@ func broadcastSessionMessage(session *model.Session, message model.Message) {
 
 func broadcastSessionUpdate(session *model.Session) {
 	payload, err := ws.NewEvent("session_updated", session.ID, gin.H{"status": session.Status})
-	if err == nil {
-		ws.DefaultHub.BroadcastToTenantStaff(session.TenantID, payload)
+	if err != nil {
+		return
 	}
+	// 坐席列表需要刷新；访客也必须收到 ended/active，才能弹出评价或更新接待状态
+	ws.DefaultHub.BroadcastToTenantStaff(session.TenantID, payload)
+	ws.DefaultHub.BroadcastToVisitor(session.TenantID, session.ID, payload)
 }
 
 func loadAssignableAgent(tenantID, agentID uint) error {
@@ -351,7 +355,79 @@ func (h *SessionHandler) Get(c *gin.Context) {
 	var pendingCount int64
 	model.DB.Model(&model.Session{}).Where("customer_id = ? AND tenant_id = ? AND status = ?", session.CustomerID, session.TenantID, "waiting").Count(&pendingCount)
 
-	middleware.JSON(c, gin.H{"session": session, "messages": messages, "events": events, "pending_count": pendingCount})
+	maxSeq := 0
+	for _, m := range messages {
+		if m.Seq > maxSeq {
+			maxSeq = m.Seq
+		}
+	}
+	middleware.JSON(c, gin.H{
+		"session":       session,
+		"messages":      messages,
+		"events":        events,
+		"pending_count": pendingCount,
+		"max_seq":       maxSeq,
+	})
+}
+
+// ListMessages 按 seq 增量拉取消息：after_seq 之后的新消息（重连 catch-up）。
+// GET /sessions/:id/messages?after_seq=12
+func (h *SessionHandler) ListMessages(c *gin.Context) {
+	session, ok := loadTenantSession(c, c.Param("id"))
+	if !ok {
+		return
+	}
+	if !canReadSession(c, session) {
+		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权查看该会话消息"})
+		return
+	}
+
+	afterSeq := 0
+	if raw := strings.TrimSpace(c.Query("after_seq")); raw != "" {
+		parsed, err := strconv.Atoi(raw)
+		if err != nil || parsed < 0 {
+			c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "after_seq 无效"})
+			return
+		}
+		afterSeq = parsed
+	}
+
+	limit := 200
+	if raw := strings.TrimSpace(c.Query("limit")); raw != "" {
+		if parsed, err := strconv.Atoi(raw); err == nil && parsed > 0 {
+			if parsed > 500 {
+				parsed = 500
+			}
+			limit = parsed
+		}
+	}
+
+	query := model.DB.Where("session_id = ?", session.ID)
+	if afterSeq > 0 {
+		query = query.Where("seq > ?", afterSeq)
+	}
+
+	var messages []model.Message
+	if err := query.Order("seq asc").Limit(limit).Find(&messages).Error; err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "查询消息失败"})
+		return
+	}
+
+	var maxSeq int
+	if err := model.DB.Model(&model.Message{}).
+		Where("session_id = ?", session.ID).
+		Select("COALESCE(MAX(seq), 0)").
+		Scan(&maxSeq).Error; err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "查询消息失败"})
+		return
+	}
+
+	middleware.JSON(c, gin.H{
+		"messages":  messages,
+		"after_seq": afterSeq,
+		"max_seq":   maxSeq,
+		"has_more":  len(messages) >= limit && (len(messages) == 0 || messages[len(messages)-1].Seq < maxSeq),
+	})
 }
 
 func (h *SessionHandler) MarkRead(c *gin.Context) {