Document HeartMuLa test routing and timing

experiments/heartmula-3b/README.md

@@ -39,7 +39,10 @@ docker compose up -d heartmula-test
 docker compose logs -f heartmula-test
 ```
 
-The temporary test UI is then available on port `7863`. Stop it with:
+The temporary test UI listens locally on port `7863`. During the listening
+test it is proxied through Athena's existing WireGuard gateway; permanent
+dashboard/gateway integration is deliberately deferred until the audio has
+been accepted. Stop it with:
 
 ```sh
 docker compose down