4.1 routing quality + 4.4 persona prompt

- VoiceConfig: add QueryMinScore (default 0.55) + Persona config fields
- voice.go: remove queryMinScore const, wire from cfg.Voice.QueryMinScore
  as reactiveHandler field
- llmphraser.go: add Persona to Config, prepend to system prompts in
  chat and query paths (systemPrompt/querySystemPrompt methods)
- main.go: pass personaFromCfg into both phraser config blocks
- Makefile: add download-embedder target (Xenova/paraphrase-multilingual-
  MiniLM-L12-v2, ~90MB ONNX)
- AGENTS.md: document embedder model download + libonnxruntime setup
- server.go: fix pre-existing wg.Add vs wg.Wait data race using accept
  mutex. make test green, zero races across all 29 packages.

internal/ipc/server.go

@@ -281,9 +281,10 @@ type Server struct {
 	api  atomic.Value // stores CoreAPI
 	path string
 
-	ln   net.Listener
-	wg   sync.WaitGroup
-	done chan struct{}
+	ln     net.Listener
+	wg     sync.WaitGroup
+	done   chan struct{}
+	accept sync.Mutex // guards wg.Add vs Close's wg.Wait sequence
 
 	// Check — optional authorization hook. dispatch runs it BEFORE method
 	// dispatch, with the raw params, so the auth layer can make verdicts
@@ -385,7 +386,12 @@ func (s *Server) Serve() error {
 				return fmt.Errorf("ipc: accept: %w", err)
 			}
 		}
+		// wg.Add under accept mutex so Close's wg.Wait (also under accept) sees
+		// a consistent counter — a connection accepted just before Close closes
+		// the listener must be tracked before Wait starts.
+		s.accept.Lock()
 		s.wg.Add(1)
+		s.accept.Unlock()
 		go func(c net.Conn) {
 			defer s.wg.Done()
 			defer c.Close()
@@ -747,7 +753,14 @@ func (s *Server) Close() error {
 		close(s.done)
 	}
 	err := s.ln.Close()
+	// Under accept lock: after the listener closes, no new Accept can complete,
+	// so no new wg.Add will be called. The Wait is safe to observe the wg
+	// counter because any in-flight Accept that already got a conn either
+	// already called wg.Add (before releasing the lock) or will see the closed
+	// listener error and not call wg.Add at all.
+	s.accept.Lock()
 	s.wg.Wait()
+	s.accept.Unlock()
 	_ = os.Remove(s.path)
 	return err
 }