feat: 下沉知识库检索编排能力

- 新增 rag retrieval 核心协议、RRF 融合与相关度归一化

- 支持关键词检索按 knowledgeId 过滤并补充 ES/Lucene 单测

- 扩展 KnowledgeNode 检索模式与 Milvus 检索参数透传

easy-agents-flow/src/main/java/com/easyagents/flow/core/node/KnowledgeNode.java

@@ -35,6 +35,7 @@ public class KnowledgeNode extends BaseNode {
     private Object knowledgeId;
     private String keyword;
     private String limit;
+    private String retrievalMode = "HYBRID";
 
     public Object getKnowledgeId() {
         return knowledgeId;
@@ -60,6 +61,14 @@ public class KnowledgeNode extends BaseNode {
         this.limit = limit;
     }
 
+    public String getRetrievalMode() {
+        return retrievalMode;
+    }
+
+    public void setRetrievalMode(String retrievalMode) {
+        this.retrievalMode = StringUtil.hasText(retrievalMode) ? retrievalMode : "HYBRID";
+    }
+
     @Override
     public Map<String, Object> execute(Chain chain) {
         Map<String, Object> argsMap = chain.getState().resolveParameters(this);
@@ -90,6 +99,7 @@ public class KnowledgeNode extends BaseNode {
                 "knowledgeId=" + knowledgeId +
                 ", keyword='" + keyword + '\'' +
                 ", limit='" + limit + '\'' +
+                ", retrievalMode='" + retrievalMode + '\'' +
                 ", parameters=" + parameters +
                 ", outputDefs=" + outputDefs +
                 ", id='" + id + '\'' +

easy-agents-flow/src/main/java/com/easyagents/flow/core/parser/impl/KnowledgeNodeParser.java

@@ -27,6 +27,7 @@ public class KnowledgeNodeParser extends BaseNodeParser<KnowledgeNode> {
         knowledgeNode.setKnowledgeId(data.get("knowledgeId"));
         knowledgeNode.setLimit(data.getString("limit"));
         knowledgeNode.setKeyword(data.getString("keyword"));
+        knowledgeNode.setRetrievalMode(data.getString("retrievalMode"));
 
         return knowledgeNode;
     }