fix: align vectorstore live retrieval

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

@@ -106,7 +106,7 @@ public class VectorSearchService {
             result.setMetadata(toJson(document.getMetadata()));
             result.setRawScore(document.getScore());
             result.setScoreLabel("similarity");
-            result.setScore(toCompatibleL2Distance(document.getScore()));
+            result.setScore(toCompatibleL2Distance(document));
             results.add(result);
         }
         logger.info("Spring AI VectorStore search complete, candidates={}", results.size());
@@ -166,6 +166,14 @@ public class VectorSearchService {
         }
     }
 
+    private float toCompatibleL2Distance(Document document) {
+        Double distance = extractDistance(document.getMetadata());
+        if (distance != null) {
+            return distance.floatValue();
+        }
+        return toCompatibleL2Distance(document.getScore());
+    }
+
     private float toCompatibleL2Distance(Double similarity) {
         if (similarity == null) {
             return (float) maxL2Distance;
@@ -174,6 +182,24 @@ public class VectorSearchService {
         return (float) ((1.0 - bounded) * maxL2Distance);
     }
 
+    private Double extractDistance(Map<String, Object> metadata) {
+        if (metadata == null) {
+            return null;
+        }
+        Object value = metadata.get("distance");
+        if (value instanceof Number number) {
+            return number.doubleValue();
+        }
+        if (value instanceof String text) {
+            try {
+                return Double.parseDouble(text);
+            } catch (NumberFormatException ignored) {
+                return null;
+            }
+        }
+        return null;
+    }
+
     private String toJson(Map<String, Object> metadata) {
         if (metadata == null || metadata.isEmpty()) {
             return null;
@@ -196,8 +222,8 @@ public class VectorSearchService {
         private String content;
         /**
          * Compatibility score used by existing lookup relevance normalization.
-         * SDK mode keeps L2 distance; VectorStore mode maps similarity into a
-         * L2-like distance using retrieval.normalization.max-l2-distance.
+         * SDK mode keeps L2 distance; VectorStore mode prefers the Milvus
+         * distance metadata and falls back to similarity mapping.
          */
         private float score;
         private Double rawScore;