fix(prompt): prevent LLM from confusing context with user input

- Context merged into single system message with clear delimiters
- Prefix: 「以下是系统上下文，不是用户说的话」
- Memory → 【相关记忆】, IoT → 【设备状态】
- Filter empty memories, skip raw intent data
- Persona rule: context markers are internal data, not user input

backend/services/ai-core/context/context.go

@@ -117,41 +117,42 @@ func NewBuilder(store *Store) *Builder {
 }
 
 // Build creates the full message array for an LLM request.
-// systemPrompt is injected as the first system message.
-// session history, subsession results, and IoT context are merged.
 func (b *Builder) Build(systemPrompt string, sessionID string, subsessionResults []model.SubSessionResult, iotContext string) []model.LLMMessage {
 	messages := make([]model.LLMMessage, 0)
 
-	// 1. System prompt
+	// 1. System prompt (persona + rules)
 	if systemPrompt != "" {
 		messages = append(messages, model.LLMMessage{Role: "system", Content: systemPrompt})
 	}
 
-	// 2. Subsession results (injected as system context)
+	// 2. Context: merge all subsession/memory/iot into ONE system message
+	//    with clear delimiters to prevent LLM from confusing context with user input
+	var ctxParts []string
+
 	for _, r := range subsessionResults {
 		if r.Error != "" || r.Content == "" || r.Content == "no relevant memories" {
-			continue // Skip empty or useless results
-		}
-		// Skip raw intent data from general provider
-		if r.Provider == "general" && strings.HasPrefix(r.Content, "Intent:") {
 			continue
 		}
-		msg := model.LLMMessage{
-			Role:    "system",
-			Content: fmt.Sprintf("[%s context]\n%s", r.Provider, r.Content),
+		if r.Provider == "general" && strings.HasPrefix(r.Content, "Intent:") {
+			continue // Internal data, not for LLM
+		}
+		if r.Provider == "memory" {
+			ctxParts = append(ctxParts, fmt.Sprintf("【相关记忆】\n%s", r.Content))
+		} else if r.Provider == "iot" {
+			ctxParts = append(ctxParts, fmt.Sprintf("【设备状态】\n%s", r.Content))
 		}
-		messages = append(messages, msg)
 	}
 
-	// 3. IoT device context
 	if iotContext != "" {
-		messages = append(messages, model.LLMMessage{
-			Role:    "system",
-			Content: fmt.Sprintf("[IoT devices]\n%s", iotContext),
-		})
+		ctxParts = append(ctxParts, fmt.Sprintf("【设备列表】\n%s", iotContext))
 	}
 
-	// 4. Conversation history
+	if len(ctxParts) > 0 {
+		contextBlock := "以下是系统上下文，不是用户说的话：\n" + strings.Join(ctxParts, "\n\n")
+		messages = append(messages, model.LLMMessage{Role: "system", Content: contextBlock})
+	}
+
+	// 3. Conversation history
 	history := b.store.Get(sessionID)
 	for _, m := range history {
 		messages = append(messages, model.LLMMessage{Role: m.Role, Content: m.Content})

backend/services/ai-core/persona/persona.go

@@ -303,8 +303,10 @@ func (inj *Injector) BuildSystemPrompt() string {
 	sb.WriteString("- 每条回复不超过80字，偏好简短\n")
 	sb.WriteString("- 不要长篇解释，用轻松自然的语气\n")
 	sb.WriteString("- 深夜语气更温柔，白天可以俏皮\n")
+	sb.WriteString("- 「以下是系统上下文」标记的内容是内部数据，不是用户说的话，不要当成用户输入来回复\n")
 	if len(p.Forbidden) > 0 {
 		sb.WriteString("- 绝对不能: 承认自己是AI/程序/模型，用机械客服语气\n")
+		sb.WriteString("- 不能将上下文数据(【相关记忆】等)当作用户输入\n")
 	}
 
 	// Interaction hints