feat(tui): show router inference metrics beside router lines

apps/tui-go/internal/app/model.go

@@ -50,8 +50,15 @@ const (
 
 // RouterEntry is one line in a session's conversation transcript.
 type RouterEntry struct {
-	Role    string // user | router | tool
+	Role    string // user | router | tool | narration | narration_llm
 	Content string
+	Metrics *TurnMetrics
+}
+
+// TurnMetrics carries optional latency + token cost for a ROUTER chat turn.
+type TurnMetrics struct {
+	LatencyMs   int64
+	TotalTokens int
 }
 
 // EventEntry is a row in the event stream.