fix chat session traces and document paths

src/main/java/com/superbiz/agent/domain/model/SessionContext.java

@@ -8,7 +8,9 @@ import lombok.NoArgsConstructor;
 import java.io.Serializable;
 import java.time.LocalDateTime;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * 会话上下文数据类
@@ -53,6 +55,12 @@ public class SessionContext implements Serializable {
     @Builder.Default
     private List<ToolCall> toolCalls = new ArrayList<>();
 
+    /**
+     * 聊天消息历史：[{"role":"user","content":"..."}, {"role":"assistant","content":"..."}]
+     */
+    @Builder.Default
+    private List<Map<String, String>> messageHistory = new ArrayList<>();
+
     /**
      * 会话创建时间
      */
@@ -79,6 +87,64 @@ public class SessionContext implements Serializable {
         this.lastActiveAt = LocalDateTime.now();
     }
 
+    /**
+     * 添加一对聊天消息，并按消息对数裁剪窗口。
+     */
+    public void addChatMessagePair(String userQuestion, String assistantAnswer, int maxPairCount) {
+        if (this.messageHistory == null) {
+            this.messageHistory = new ArrayList<>();
+        }
+
+        Map<String, String> userMessage = new HashMap<>();
+        userMessage.put("role", "user");
+        userMessage.put("content", userQuestion);
+        this.messageHistory.add(userMessage);
+
+        Map<String, String> assistantMessage = new HashMap<>();
+        assistantMessage.put("role", "assistant");
+        assistantMessage.put("content", assistantAnswer);
+        this.messageHistory.add(assistantMessage);
+
+        int maxMessages = Math.max(maxPairCount, 0) * 2;
+        while (maxMessages > 0 && this.messageHistory.size() > maxMessages) {
+            this.messageHistory.remove(0);
+            if (!this.messageHistory.isEmpty()) {
+                this.messageHistory.remove(0);
+            }
+        }
+        this.lastActiveAt = LocalDateTime.now();
+    }
+
+    /**
+     * 获取聊天历史副本，避免调用方直接修改内部列表。
+     */
+    public List<Map<String, String>> getMessageHistorySnapshot() {
+        if (this.messageHistory == null || this.messageHistory.isEmpty()) {
+            return new ArrayList<>();
+        }
+        List<Map<String, String>> snapshot = new ArrayList<>();
+        for (Map<String, String> message : this.messageHistory) {
+            snapshot.add(new HashMap<>(message));
+        }
+        return snapshot;
+    }
+
+    /**
+     * 清空聊天历史。
+     */
+    public void clearMessageHistory() {
+        if (this.messageHistory == null) {
+            this.messageHistory = new ArrayList<>();
+        } else {
+            this.messageHistory.clear();
+        }
+        this.lastActiveAt = LocalDateTime.now();
+    }
+
+    public int getMessagePairCount() {
+        return this.messageHistory == null ? 0 : this.messageHistory.size() / 2;
+    }
+
     /**
      * 更新最后活跃时间
      */