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).

.mcp.json

@@ -1,12 +1,16 @@
 {
   "mcpServers": {
     "jupyter": {
-      "command": "/home/enmanuel/fn_registry/analysis/nats/.venv/bin/jupyter-mcp-server",
+      "command": "bash",
       "args": [
-        "--transport", "stdio",
-        "--jupyter-url", "http://localhost:8890",
-        "--jupyter-token", ""
-      ]
+        "/home/enmanuel/fn_registry/bash/functions/infra/jupyter_mcp_serve.sh"
+      ],
+      "env": {
+        "JUPYTER_MCP_VENV": "/home/enmanuel/fn_registry/analysis/nats/.venv",
+        "JUPYTER_MCP_ROOT": "/home/enmanuel/fn_registry/analysis/nats",
+        "JUPYTER_MCP_PORT": "8890",
+        "JUPYTER_MCP_TOKEN": ""
+      }
     }
   }
 }