feat(aihr): return explicit no-evidence SOP answers and log knowledge gaps

- Empty/unanswerable SOP queries now return the fixed 「未在已入库 SOP 中找到明确依据」
  response instead of falling back to seed answers (no fake answers)
- Record knowledge_gap (question/category/position/source) whenever search
  yields no evidence — feeds the phase-two open question board
- Extract NO_CLEAR_SOP_EVIDENCE constant shared by digest prompt and checks

backend/ruoyi-modules/ruoyi-aihr/src/main/java/org/dromara/aihr/service/AihrSopSeedService.java

@@ -91,6 +91,7 @@ public class AihrSopSeedService {
     private static final String LOCAL_EMBEDDING_MODEL = "local-hash-v1";
     private static final String LOCAL_EMBEDDING_BASE_URL = "local";
     private static final int LOCAL_EMBEDDING_DIMENSION = 1536;
+    private static final String NO_CLEAR_SOP_EVIDENCE = "未在已入库 SOP 中找到明确依据";
     private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
 
     private final Map<String, SopSeed> seeds = buildSeeds();
@@ -120,25 +121,19 @@ public class AihrSopSeedService {
         String category = isBlank(requestedCategory) ? seed.category() : requestedCategory;
         String position = firstNonBlank(request == null ? null : request.position(), "生活顾问");
         String source = normalizeSearchSource(request == null ? null : request.source());
-        String queryText = request == null || request.queryText() == null || request.queryText().isBlank() ? seed.question() : request.queryText();
+        String queryText = request == null ? "" : Optional.ofNullable(request.queryText()).orElse("").trim();
+        if (isBlank(queryText)) {
+            return withReviewId(noEvidenceResponse("", category), source);
+        }
         SearchResponse dbResponse = dbSearch(dbCategory(category), queryText, request == null ? null : request.limit());
-        if (dbResponse != null && !dbResponse.snippets().isEmpty()) {
+        if (dbResponse != null) {
+            if (isNoEvidenceAnswer(dbResponse.answer())) {
+                recordKnowledgeGap(queryText, category, position, source);
+            }
             return withReviewId(dbResponse, source);
         }
         recordKnowledgeGap(queryText, category, position, source);
-        return withReviewId(new SearchResponse(
-            queryText,
-            seed.category(),
-            seed.answer(),
-            seed.reference(),
-            seed.docs(),
-            seed.snippets(),
-            seed.training(),
-            records(),
-            List.of(),
-            List.of(),
-            null
-        ), source);
+        return withReviewId(noEvidenceResponse(queryText, category), source);
     }
 
     public SopReviewResponse reviewSearch(Long id, SopReviewRequest request) {
@@ -2003,17 +1998,23 @@ public class AihrSopSeedService {
             docs.putIfAbsent(hit.title(), new DocResponse(hit.title(), hit.description(), "命中 " + scoreText(hit.score()), "pill-success"));
         }
         SearchDigest digest = searchDigest(queryText, hits);
+        if (digest == null) {
+            return noEvidenceResponse(queryText, responseCategory);
+        }
+        if (isNoEvidenceAnswer(digest.answer())) {
+            return noEvidenceResponse(queryText, responseCategory, digest.cautions());
+        }
         return new SearchResponse(
             queryText,
             responseCategory,
-            digest != null ? digest.answer() : "根据已入库 SOP：" + first.content(),
+            digest.answer(),
             "引用 " + docs.size() + " 份文档 / " + snippets.size() + " 个片段",
             List.copyOf(docs.values()),
             snippets,
             List.of("题 1：请按命中 SOP 复述处理步骤。", "题 2：哪些信息必须留痕并可追溯？"),
             records(),
-            digest != null ? digest.keyPoints() : List.of(),
-            digest != null ? digest.cautions() : List.of(),
+            digest.keyPoints(),
+            digest.cautions(),
             null
         );
     }
@@ -2063,7 +2064,7 @@ public class AihrSopSeedService {
         system.put("content", "你是物业一线员工的SOP助手。只返回 JSON，不要 markdown。字段固定为 answer, keyPoints, cautions。"
             + "answer 是对问题的直接回答（不超过60字，含关键数字/时限）；keyPoints 是3到6条可执行要点（每条一句话，含具体数字）；"
             + "cautions 是0到3条注意事项或红线。硬约束：只能基于给定片段内容作答，片段中没有的信息不得编造；"
-            + "若片段无法回答问题，answer 固定为「未在已入库 SOP 中找到明确依据」且 keyPoints 为空数组。");
+            + "若片段无法回答问题，answer 固定为「" + NO_CLEAR_SOP_EVIDENCE + "」且 keyPoints 为空数组。");
 
         ObjectNode user = messages.addObject();
         user.put("role", "user");
@@ -2247,6 +2248,30 @@ public class AihrSopSeedService {
         return score <= 0 ? "片段" : String.format("%.2f", score);
     }
 
+    private static boolean isNoEvidenceAnswer(String answer) {
+        return NO_CLEAR_SOP_EVIDENCE.equals(Optional.ofNullable(answer).orElse("").trim());
+    }
+
+    private static SearchResponse noEvidenceResponse(String queryText, String category) {
+        return noEvidenceResponse(queryText, category, List.of());
+    }
+
+    private static SearchResponse noEvidenceResponse(String queryText, String category, List<String> cautions) {
+        return new SearchResponse(
+            queryText,
+            firstNonBlank(category, "sop"),
+            NO_CLEAR_SOP_EVIDENCE,
+            "未找到可引用片段",
+            List.of(),
+            List.of(),
+            List.of(),
+            records(),
+            List.of(),
+            cautions,
+            null
+        );
+    }
+
     private KnowledgeConfig knowledgeConfig(String category) {
         List<KnowledgeConfig> rows = jdbcTemplate.query("""
             select id, coalesce(text_block_size, 800) as block_size, coalesce(overlap_char, 120) as overlap_char