refactor: output channel interface (payload/meta/type) + memory fixes

- Redesign output_send__ tools: content JSON string -> structured
  payload/meta/type params for LLM reliability
- executeOutputSendTool: route by type with capability check
- executeOutputSendHelp: show meta format + type enum
- Updated system prompt rules for new interface
- docToTriples: use jieba exact mode adjacent co-occurrence
- Unify vector space: Doc.Vector field, ContextToDoc vectorizer,
  ReindexWithVectorizer on startup

internal/memory/document/document_test.go

@@ -82,7 +82,7 @@ func TestContextToDoc(t *testing.T) {
 		{Timestamp: time.Now(), Source: "user", Content: "特别是Go语言", Response: "Go很棒"},
 	}
 
-	doc, err := s.ContextToDoc("test", entries)
+	doc, err := s.ContextToDoc("test", entries, nil)
 	if err != nil {
 		t.Fatal(err)
 	}