fix: 消息日志增强 + 历史消息抑制 + SSE实时追踪 + 群聊上下文优化

- 日志：收/发消息均显示群名称，管理员显示真实QQ昵称而非"开拓者"
- 历史消息：服务重启后NapCat回放的历史消息不再触发回复，静默注入上下文
- 消息时间戳：转发给AI时附带【消息时间: HH:MM:SS (XmXs前)】标记
- ♪ 分割符：QQ消息支持♪作为句子断点
- AI-Core SSE端点：全链路追踪实时推送，ethend不再5秒轮询
- 群聊上下文：AI-Core明确被告知消息来自群聊，以实际发送者为主语

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/platform-bridge/cmd/main.go

@@ -75,7 +75,8 @@ func main() {
 			Platform:    msg.Platform,
 			ChannelID:   msg.ChannelID,
 			SenderID:    msg.OriginalSenderUID,
-			SenderName:  msg.SenderName,
+			SenderName:  msg.OriginalSenderName,
+			GroupName:   msg.GroupName,
 			Content:     msg.Content,
 			ContentType: msg.ContentType,
 			MessageID:   msg.MessageID,
@@ -88,6 +89,29 @@ func main() {
 		isBotMentioned := msg.BotUID != "" && containsString(msg.Mentions, msg.BotUID)
 		isSilent := cfg.PlatformSilentEnabled && !isAdmin && !isBotMentioned
 
+		// Add message timestamp for AI context.
+		if !msg.Timestamp.IsZero() {
+			timeAgo := time.Since(msg.Timestamp)
+			timeLabel := fmt.Sprintf("【消息时间: %s (%s前)】\n", msg.Timestamp.Format("15:04:05"), formatDuration(timeAgo))
+			msg.Content = timeLabel + msg.Content
+		}
+
+		// Enrich group messages with group name and sender info.
+		if msg.ChannelType == "group" {
+			groupLabel := msg.ChannelID
+			if msg.GroupName != "" {
+				groupLabel = truncateString(msg.GroupName, 8) + " " + msg.ChannelID
+			}
+			senderLabel := msg.OriginalSenderName
+			if senderLabel == "" {
+				senderLabel = msg.SenderName
+			}
+			if isAdmin {
+				senderLabel = "【管理员】" + msg.OriginalSenderName
+			}
+			msg.Content = fmt.Sprintf("[群聊 %s] %s (%s)：\n%s", groupLabel, senderLabel, msg.OriginalSenderUID, msg.Content)
+		}
+
 		// Blocklist/whitelist check (admin always bypasses).
 		if blocked := blocklistStore.IsBlocked(msg.ChannelType, msg.ChannelID, msg.OriginalSenderUID, isAdmin); blocked {
 			msgLogger.Log(logging.LogEntry{
@@ -122,6 +146,11 @@ func main() {
 		groupSessionID := fmt.Sprintf("platform_%s_%s", msg.Platform, msg.ChannelID)
 
 		switch {
+		case isMessageHistorical(msg, router):
+			msg.RouteType = "silent"
+			namespace := buildMemoryNamespace(msg.Platform, msg.ChannelType, msg.ChannelID)
+			response, routeErr = forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, nil)
+
 		case isAdmin && !isBotMentioned && shouldAdminBeSilent(msg, router):
 			msg.RouteType = "silent"
 			namespace := buildMemoryNamespace(msg.Platform, msg.ChannelType, msg.ChannelID)
@@ -189,6 +218,7 @@ func main() {
 					ChannelID:   msg.ChannelID,
 					SenderID:    msg.BotUID,
 					SenderName:  "Cyrene",
+					GroupName:   msg.GroupName,
 					Content:     rm.Content,
 					ContentType: "text",
 					Success:     true,
@@ -678,20 +708,30 @@ func parseSSEAndAccumulate(body string) string {
 	return strings.Join(deltas, "")
 }
 
-// splitContent splits text by \n\n into multiple ResponseMessage segments.
+// splitContent splits text by ♪ (sentence-break marker), then by \n\n within each segment.
 // Non-empty segments are each wrapped as a chat message; empty input returns a single empty message.
 func splitContent(text string) []bridge.ResponseMessage {
-	parts := strings.Split(text, "\n\n")
+	// First split by ♪ sentence-break marker.
+	var rawParts []string
+	if strings.Contains(text, "♪") {
+		rawParts = strings.Split(text, "♪")
+	} else {
+		rawParts = strings.Split(text, "\n\n")
+	}
+	var parts []string
+	for _, p := range rawParts {
+		p = strings.TrimSpace(p)
+		if p != "" {
+			parts = append(parts, p)
+		}
+	}
 	var msgs []bridge.ResponseMessage
 	for _, part := range parts {
-		part = strings.TrimSpace(part)
-		if part != "" {
-			msgs = append(msgs, bridge.ResponseMessage{
-				DisplayType: "chat",
-				Content:     part,
-				FormatMode:  "plain",
-			})
-		}
+		msgs = append(msgs, bridge.ResponseMessage{
+			DisplayType: "chat",
+			Content:     part,
+			FormatMode:  "plain",
+		})
 	}
 	if len(msgs) == 0 {
 		return []bridge.ResponseMessage{
@@ -843,3 +883,49 @@ func syncAdminUIDs(m *bridge.IdentityMapper, platform string, fields map[string]
 	}
 	fmt.Printf("Synced admin identities for %s from config: %s\n", platform, raw)
 }
+
+// formatDuration returns a human-readable duration string like "1h2m3s".
+func formatDuration(d time.Duration) string {
+	if d < time.Minute {
+		return fmt.Sprintf("%ds", int(d.Seconds()))
+	}
+	if d < time.Hour {
+		m := int(d.Minutes())
+		s := int(d.Seconds()) % 60
+		if s > 0 {
+			return fmt.Sprintf("%dm%ds", m, s)
+		}
+		return fmt.Sprintf("%dm", m)
+	}
+	h := int(d.Hours())
+	m := int(d.Minutes()) % 60
+	if m > 0 {
+		return fmt.Sprintf("%dh%dm", h, m)
+	}
+	return fmt.Sprintf("%dh", h)
+}
+
+// truncateString truncates a string to maxRunes runes, appending "…" if truncated.
+func truncateString(s string, maxRunes int) string {
+	runes := []rune(s)
+	if len(runes) <= maxRunes {
+		return s
+	}
+	return string(runes[:maxRunes]) + "…"
+}
+
+// isMessageHistorical returns true if the message timestamp is before the adapter's connection time,
+// indicating it is a replayed historical message that should be silently observed.
+func isMessageHistorical(msg *bridge.UnifiedMessage, router *bridge.PlatformRouter) bool {
+	if msg.Timestamp.IsZero() {
+		return false
+	}
+	for _, a := range router.GetAdaptersByPlatform(msg.Platform) {
+		if connectedAt, ok := a.(interface{ ConnectedAt() time.Time }); ok {
+			if msg.Timestamp.Before(connectedAt.ConnectedAt()) {
+				return true
+			}
+		}
+	}
+	return false
+}