feat(rag): 检索质量评测 —— 单路检索能力 + recall@k/MRR 评测台

- 引擎抽 searchPaths(三路召回) + SearchByMode(vector/fulltext/graph/hybrid，
  纯检索不 rerank，公平对比)；kb_search 加 mode 参数(空=生产含rerank)，
  gateway KbSearch 透传 mode
- scripts/rageval.py：标注语料+查询 → 四模式 recall@k/MRR 对比表（可复用）
- live 量化：纯语义改写让全文0.88/图谱0.75 漏召回，混合 1.00 兜回，
  混合=各路上界的稳健组合

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-mcp-go/internal/mcp/gateway.go

@@ -341,7 +341,15 @@ func (g *Gateway) kbSearch(ctx context.Context, call *contract.ToolCall) *contra
 	if !g.rag.Ready() {
 		return &contract.ToolResult{OK: true, Content: "[]"}
 	}
-	hits, err := g.rag.Search(ctx, kb, q, topK)
+	// mode 空=生产混合检索(含 rerank)；显式 vector/fulltext/graph/hybrid=评测用单路/纯融合(不 rerank)。
+	mode, _ := call.Args["mode"].(string)
+	var hits []rag.Hit
+	var err error
+	if mode == "" {
+		hits, err = g.rag.Search(ctx, kb, q, topK)
+	} else {
+		hits = g.rag.SearchByMode(ctx, kb, q, topK, mode)
+	}
 	if err != nil {
 		return &contract.ToolResult{OK: false, Error: "kb_search: " + err.Error()}
 	}

sundynix-mcp-go/internal/rag/rag.go

@@ -233,16 +233,7 @@ func (e *Engine) Search(ctx context.Context, kb, query string, topK int) ([]Hit,
 	}
 	fanout := topK * 3
 
-	// 向量路
-	vecs, err := e.embed().Embed(ctx, []string{query})
-	if err != nil || len(vecs) == 0 {
-		return nil, err
-	}
-	vecHits, _ := e.mv.search(ctx, kb, vecs[0], fanout)
-	// 全文路
-	ftHits := e.bleve.search(kb, query, fanout)
-	// 图谱路（GraphRAG：查询提到的实体的相连三元组）
-	graphHits := e.graph.search(ctx, kb, query, fanout)
+	vecHits, ftHits, graphHits := e.searchPaths(ctx, kb, query, fanout)
 	// RRF 融合（三路，按文本去重）
 	cand := rrf([][]Hit{vecHits, ftHits, graphHits}, fanout)
 	log.Printf("[rag] hybrid: 向量=%d 全文=%d 图谱=%d → 融合=%d", len(vecHits), len(ftHits), len(graphHits), len(cand))
@@ -277,6 +268,43 @@ func (e *Engine) DeleteDoc(ctx context.Context, kb, fileID string) error {
 	return nil
 }
 
+// searchPaths 跑三路召回，返回各路命中（供混合融合与离线评测按单路对比）。
+func (e *Engine) searchPaths(ctx context.Context, kb, query string, fanout int) (vec, ft, graph []Hit) {
+	if vecs, err := e.embed().Embed(ctx, []string{query}); err == nil && len(vecs) > 0 {
+		vec, _ = e.mv.search(ctx, kb, vecs[0], fanout)
+	}
+	ft = e.bleve.search(kb, query, fanout)
+	graph = e.graph.search(ctx, kb, query, fanout)
+	return
+}
+
+// SearchByMode 按指定模式返回 topK（评测用，纯检索不 rerank，便于公平对比）。
+// mode: vector|fulltext|graph|hybrid(RRF)。
+func (e *Engine) SearchByMode(ctx context.Context, kb, query string, topK int, mode string) []Hit {
+	if !e.Ready() || topK <= 0 {
+		if topK <= 0 {
+			topK = 5
+		}
+	}
+	fanout := topK * 3
+	vec, ft, graph := e.searchPaths(ctx, kb, query, fanout)
+	var hits []Hit
+	switch mode {
+	case "vector":
+		hits = vec
+	case "fulltext":
+		hits = ft
+	case "graph":
+		hits = graph
+	default: // hybrid
+		hits = rrf([][]Hit{vec, ft, graph}, fanout)
+	}
+	if len(hits) > topK {
+		hits = hits[:topK]
+	}
+	return hits
+}
+
 func (e *Engine) Close() {
 	if e.mv != nil {
 		e.mv.close()