feat(session): 会话存储体系实现 & Chat多Agent路由

- 新增诊断会话(diagnosis_session/agent_step/tool_invocation)三表
- AgentLoggingHook 持久化 agent_step，记录决策链和耗时
- LookupKnowledgeTool 写入 tool_invocation，记录L0/L1检索质量
- TokenTrackingChatModel 捕获真实token用量
- Chat接口支持意图路由：简单问题单Agent，复杂问题多Agent(Planner+Executor)
- Prompt外置到 src/main/resources/prompts/
- 删除旧 diagnosis_record 表及相关文件
- 新增SessionContextHolder(ThreadLocal传递sessionId)
- QuestionComplexity 复杂度判断工具
- 测试覆盖三张新表的Repository

src/main/java/com/superbiz/agent/tool/LookupKnowledgeTool.java

@@ -1,8 +1,11 @@
 package com.superbiz.agent.tool;
 
+import com.superbiz.agent.domain.entity.ToolInvocation;
 import com.superbiz.agent.dto.*;
+import com.superbiz.agent.repository.ToolInvocationRepository;
 import com.superbiz.agent.service.KnowledgeIndexService;
 import com.superbiz.agent.service.VectorSearchService;
+import com.superbiz.agent.util.SessionContextHolder;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.ai.tool.annotation.Tool;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -25,6 +28,9 @@ public class LookupKnowledgeTool {
     @Autowired
     private VectorSearchService vectorSearchService;
 
+    @Autowired
+    private ToolInvocationRepository toolInvocationRepository;
+
     /**
      * 查询知识库文档
      *
@@ -134,9 +140,120 @@ public class LookupKnowledgeTool {
 
         log.info("========================================");
 
+        // 记录 tool_invocation（持久化检索明细）
+        saveToolInvocation(query, l0Matches, l1Results, highConfidence, startTime, result);
+
         return result;
     }
 
+    /**
+     * 保存工具调用明细到 tool_invocation 表
+     */
+    private void saveToolInvocation(String query, List<KnowledgeEntry> l0Matches,
+                                    List<VectorSearchService.SearchResult> l1Results,
+                                    boolean highConfidence, long startTime, LookupResult result) {
+        try {
+            String sessionId = SessionContextHolder.getSessionId();
+            if (sessionId == null) return; // 非会话上下文不记录
+
+            boolean hasL0 = l0Matches != null && !l0Matches.isEmpty();
+            boolean hasL1 = l1Results != null && !l1Results.isEmpty();
+            long duration = System.currentTimeMillis() - startTime;
+
+            String layer;
+            String outputPreview = null;
+            int outputLength = 0;
+            int l0Count = 0;
+            int l1Count = 0;
+            boolean truncated = false;
+
+            if (hasL0 && !highConfidence) {
+                layer = "L0+L1";
+                l0Count = l0Matches.size();
+                l1Count = l1Results.size();
+            } else if (hasL0) {
+                layer = "L0";
+                l0Count = l0Matches.size();
+            } else if (hasL1) {
+                layer = "L1";
+                l1Count = l1Results.size();
+            } else {
+                layer = null;
+            }
+
+            // 拼接 output_preview（前500字符）
+            if (result != null && result.getPrimary() != null && result.getPrimary().getContent() != null) {
+                String content = result.getPrimary().getContent();
+                outputLength = content.length();
+                if (content.length() > 500) {
+                    outputPreview = content.substring(0, 500) + "...";
+                    truncated = true;
+                } else {
+                    outputPreview = content;
+                }
+            } else if (l1Results != null && !l1Results.isEmpty() && l1Results.get(0).getContent() != null) {
+                String content = l1Results.get(0).getContent();
+                outputLength = content.length();
+                if (content.length() > 500) {
+                    outputPreview = content.substring(0, 500) + "...";
+                    truncated = true;
+                } else {
+                    outputPreview = content;
+                }
+            }
+
+            // 构建检索明细 JSON
+            StringBuilder details = new StringBuilder("{");
+            if (hasL0) {
+                details.append("\"l0_titles\":[");
+                for (int i = 0; i < Math.min(3, l0Matches.size()); i++) {
+                    if (i > 0) details.append(",");
+                    details.append("\"").append(escapeJson(l0Matches.get(i).getTitle())).append("\"");
+                }
+                details.append("]");
+            }
+            if (hasL1) {
+                if (hasL0) details.append(",");
+                details.append("\"l1_scores\":[");
+                for (int i = 0; i < Math.min(3, l1Results.size()); i++) {
+                    if (i > 0) details.append(",");
+                    details.append(l1Results.get(i).getScore());
+                }
+                details.append("]");
+            }
+            details.append("}");
+
+            ToolInvocation inv = ToolInvocation.builder()
+                    .sessionId(sessionId)
+                    .toolName("lookup_knowledge")
+                    .inputParams("{\"query\":\"" + escapeJson(query) + "\"}")
+                    .outputPreview(outputPreview)
+                    .outputLength(outputLength)
+                    .retrievalLayer(layer)
+                    .l0MatchCount(hasL0 ? l0Count : null)
+                    .l1MatchCount(hasL1 ? l1Count : null)
+                    .isTruncated(truncated)
+                    .retrievalDetails(details.toString())
+                    .durationMs((int) duration)
+                    .success(true)
+                    .build();
+
+            toolInvocationRepository.save(inv);
+            log.debug("tool_invocation 已保存: sessionId={}, layer={}, duration={}ms", sessionId, layer, duration);
+        } catch (Exception e) {
+            log.error("保存 tool_invocation 失败", e);
+        }
+    }
+
+    private String escapeJson(String s) {
+        if (s == null) return "";
+        return s.replace("\\", "\\\\")
+                .replace("\"", "\\\"")
+                .replace("\n", "\\n")
+                .replace("\r", "\\r")
+                .replace("\t", "\\t");
+    }
+
     /**
      * 组装查询结果
      *