feat(rag): pgvector knowledge base with API and LLM tools

- services/rag: knowledge_docs store — vector search via the shared
  embedder (HNSW index, graceful ILIKE fallback), list/delete scoped to
  the user, search intentionally global for the single-user deployment
- gateway: GET/POST /knowledge/docs, DELETE /knowledge/docs/:id,
  POST /knowledge/search
- plugins/knowledge: knowledge_search and knowledge_ingest tools so the
  persona can save and recall information mid-conversation
- main: migrations, store wiring, plugin registration

backend/cmd/cyrene/main.go

@@ -32,6 +32,7 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/plugins/text"
 	webfetch "git.yeij.top/AskaEth/Cyrene_v2/plugins/web-fetch"
 	websearch "git.yeij.top/AskaEth/Cyrene_v2/plugins/web-search"
+	"git.yeij.top/AskaEth/Cyrene_v2/plugins/knowledge"
 
 	"git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/background"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/emotion"
@@ -49,6 +50,7 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/services/gateway/store"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/gateway/ws"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/memory"
+	"git.yeij.top/AskaEth/Cyrene_v2/services/rag"
 	bridge "git.yeij.top/AskaEth/Cyrene_v2/services/platform-bridge"
 	bridgeqq "git.yeij.top/AskaEth/Cyrene_v2/services/platform-bridge/qq"
 	bridgetg "git.yeij.top/AskaEth/Cyrene_v2/services/platform-bridge/telegram"
@@ -146,6 +148,7 @@ func main() {
 
 	// === 6. Memory Service ===
 	var memSvc *memory.Service
+	var ragStore *rag.Store
 	if database != nil {
 		memRepo := memory.NewRepository(database)
 		memSvc = memory.NewService(memRepo)
@@ -160,6 +163,19 @@ func main() {
 			logger.Infof("[memory] hybrid search enabled (vector dims=%d, api=%v)", emb.Dims(), emb.IsAvailable())
 		}
 		logger.Infof("[memory] connected")
+
+		// === 6.5 Knowledge base (RAG) ===
+		db.RunMigration(context.Background(), database, "knowledge", db.SplitSQL(rag.CreateTableSQL()))
+		ragStore = rag.NewStore(database, emb)
+		if err := db.RunMigration(context.Background(), database, "knowledge-vector", db.SplitSQL(rag.VectorMigrationSQL(emb.Dims()))); err != nil {
+			logger.Infof("[rag] pgvector unavailable, ILIKE-only search: %v", err)
+		} else {
+			ragStore.EnableVector()
+		}
+		if err := reg.Register(knowledge.New(ragStore), pluginCfg); err != nil {
+			logger.Infof("[plugin] knowledge: %v", err)
+		}
+		logger.Infof("[rag] knowledge base ready")
 	} else {
 		logger.Infof("[memory] disabled (no database)")
 	}
@@ -316,6 +332,9 @@ func main() {
 	}
 	gwDeps.VoiceSvc = voiceSvc
 	gwDeps.Vision = visionAdapter{llmSelector.DefaultAdapter()}
+	if ragStore != nil {
+		gwDeps.Knowledge = ragStore
+	}
 
 	wsHub := ws.NewHub(orch)
 	gwDeps.WSHub = wsHub