feat: notebook 04 — JetStream a fondo + simulador de rendimiento interactivo

JetStream: anatomia de streams (storage/retention/limits), consumers pull durables
con ack y cursor, dedup por Nats-Msg-Id, retencion workqueue, deliver policies.
Simulador: boton ipywidgets que lanza 1 publisher -> N subscribers con miles de
mensajes y grafica en movimiento (acumulado + throughput instantaneo).

notebooks/01_core_pubsub.ipynb

@@ -427,12 +427,21 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": "NATS analysis",
    "language": "python",
-   "name": "python3"
+   "name": "nats"
   },
   "language_info": {
-   "name": ""
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.3"
   }
  },
  "nbformat": 4,