fix: 后台思考身份混淆 + 静默模式视觉理解 + QQ卡片解析 + 仪表盘状态修复

- 后台思考对话历史增加标签说明，严格区分群聊中不同发送者
- 静默观察模式传入图片URL并预处理，供后台思考参考
- 视觉+OCR双模型结果合并格式优化，避免LLM误认为多张图片
- QQ卡片消息(CQ:json)正确解析标题/类型，不再丢失为[JSON]
- 进程管理器stop()在进程为null时重置pid/startTime，消除矛盾状态

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

backend/platform-bridge/cmd/main.go

@@ -180,7 +180,7 @@ func main() {
 		case isAdmin && !isBotMentioned && shouldAdminBeSilent(msg, router):
 			msg.RouteType = "silent"
 			namespace := buildMemoryNamespace(msg.Platform, msg.ChannelType, msg.ChannelID)
-			response, routeErr = forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, nil, videoURLs, voiceURLs, isAdmin)
+			response, routeErr = forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, imageURLs, videoURLs, voiceURLs, isAdmin)
 
 		case isAdmin:
 			msg.RouteType = "normal"
@@ -195,12 +195,12 @@ func main() {
 			// the admin already gets QQ's native @notification. Observe silently.
 			msg.RouteType = "silent"
 			namespace := buildMemoryNamespace(msg.Platform, msg.ChannelType, msg.ChannelID)
-			response, routeErr = forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, nil, videoURLs, voiceURLs, isAdmin)
+			response, routeErr = forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, imageURLs, videoURLs, voiceURLs, isAdmin)
 
 		case isSilent:
 			msg.RouteType = "silent"
 			namespace := buildMemoryNamespace(msg.Platform, msg.ChannelType, msg.ChannelID)
-			silentResponse, silentErr := forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, nil, videoURLs, voiceURLs, isAdmin)
+			silentResponse, silentErr := forwardToAICore(cfg, msg, "platform_silent", namespace, namespace, imageURLs, videoURLs, voiceURLs, isAdmin)
 			if silentErr != nil {
 				msgLogger.Log(logging.LogEntry{
 					Timestamp:  time.Now(),
@@ -769,23 +769,49 @@ func parseSSEAndAccumulate(body string) string {
 	return strings.Join(deltas, "")
 }
 
-// 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.
+// splitContent splits text into separate chat messages.
+// It first splits by \n\n (message separator), then within each message
+// optionally splits further by ♪ (sentence-break marker).
+// Very short segments (< 10 chars) are merged with their neighbors to avoid
+// one-word messages followed by a wall of text.
 func splitContent(text string) []bridge.ResponseMessage {
-	// First split by ♪ sentence-break marker.
-	var rawParts []string
-	if strings.Contains(text, "♪") {
-		rawParts = strings.Split(text, "♪")
-	} else {
-		rawParts = strings.Split(text, "\n\n")
-	}
+	// Step 1: split by \n\n (message-level separator) always.
+	rawParts := strings.Split(text, "\n\n")
 	var parts []string
 	for _, p := range rawParts {
 		p = strings.TrimSpace(p)
-		if p != "" {
+		if p == "" {
+			continue
+		}
+		// Step 2: within each \n\n segment, split by ♪ if present.
+		if strings.Contains(p, "♪") {
+			for _, sub := range strings.Split(p, "♪") {
+				sub = strings.TrimSpace(sub)
+				if sub != "" {
+					parts = append(parts, sub)
+				}
+			}
+		} else {
 			parts = append(parts, p)
 		}
 	}
+
+	// Step 3: merge very short segments with neighbors.
+	const minRunes = 8
+	var merged []string
+	for _, part := range parts {
+		if len(merged) > 0 && len([]rune(merged[len(merged)-1])) < minRunes {
+			// Previous segment is too short: merge current into it.
+			merged[len(merged)-1] = merged[len(merged)-1] + "\n" + part
+		} else if len(merged) > 0 && len([]rune(part)) < minRunes {
+			// Current segment is too short: merge it into previous.
+			merged[len(merged)-1] = merged[len(merged)-1] + "\n" + part
+		} else {
+			merged = append(merged, part)
+		}
+	}
+	parts = merged
+
 	var msgs []bridge.ResponseMessage
 	for _, part := range parts {
 		msgs = append(msgs, bridge.ResponseMessage{