fix(agent): harden live diagnosis skill observability

src/main/java/com/superbiz/agent/service/ChatService.java

@@ -544,6 +544,10 @@ public class ChatService {
     private ReactAgent buildChatExecutorAgent(ChatModel chatModel, ToolCallback[] toolCallbacks,
                                               List<Map<String, String>> history, String retryContext) {
         StringBuilder prompt = new StringBuilder(chatExecutorPrompt);
+        prompt.append("\n\n--- Skill 读取约束 ---\n")
+                .append("如果 planner_plan 已给出 selected_skill，本轮 Executor 只允许对该 skill 调用一次 read_skill。")
+                .append("读取后必须复用已加载的 playbook 指令继续执行证据工具，不要为了检查支持文件、确认流程或生成报告再次读取同一个 skill。")
+                .append("只有 ChatService 启动新的补证据 retry round 时，才可以重新读取 selected_skill。\n");
         if (!history.isEmpty()) {
             prompt.append("\n\n--- 对话历史 ---\n");
             for (Map<String, String> msg : history) {
@@ -764,14 +768,29 @@ public class ChatService {
 
     private String buildLowConfidenceOutput(String executorAnswer, VerifierDecision decision) {
         StringBuilder output = new StringBuilder(LOW_CONFID_DISCLAIMER);
-        output.append("\n\n").append(executorAnswer == null ? "" : executorAnswer);
+        List<String> confirmedFacts = extractConfirmedFacts(decision);
+        output.append("\n\n已确认信息：");
+        if (confirmedFacts.isEmpty()) {
+            output.append("\n- 暂无可稳定确认的信息");
+        } else {
+            for (String fact : confirmedFacts) {
+                output.append("\n- ").append(fact);
+            }
+        }
 
         List<String> gaps = extractEvidenceGaps(decision);
+        output.append("\n\n当前缺口：");
         if (!gaps.isEmpty()) {
-            output.append("\n\n当前缺口：");
             for (String gap : gaps) {
                 output.append("\n- ").append(gap);
             }
+        } else {
+            output.append("\n- 当前缺少足够的直接证据支撑核心结论");
+        }
+
+        output.append("\n\n建议下一步：");
+        for (String suggestion : buildNextStepSuggestions(decision)) {
+            output.append("\n- ").append(suggestion);
         }
         return output.toString();
     }
@@ -813,7 +832,7 @@ public class ChatService {
         for (Map<String, Object> fact : decision.factsChecked()) {
             String verification = String.valueOf(fact.get("verification"));
             boolean critical = Boolean.TRUE.equals(fact.get("is_critical"));
-            if (critical && ("direct_evidence".equals(verification) || "indirect_support".equals(verification))) {
+            if (critical && "direct_evidence".equals(verification)) {
                 confirmedFacts.add(String.valueOf(fact.get("fact")));
             }
         }