fix(notebooks): install langchain-coordinode from git pin; add health checks to 01_llama

- 02_langchain: replace PyPI langchain-coordinode with git+https install
  from the pinned repo commit so CoordinodeGraph(client=...) constructor
  is available in Colab (PyPI v0.5.0 lacks this parameter)
- 01_llama: add client.health() guard after CoordinodeClient construction
  in both gRPC branches so the setup cell fails early when the server is
  unreachable rather than silently passing with a lazy client

Author: polaz

demo/notebooks/01_llama_index_property_graph.ipynb

@@ -169,6 +169,9 @@
     "    from coordinode import CoordinodeClient\n",
     "\n",
     "    client = CoordinodeClient(COORDINODE_ADDR)\n",
+    "    if not client.health():\n",
+    "        client.close()\n",
+    "        raise RuntimeError(f\"CoordiNode at {COORDINODE_ADDR} is not serving health checks\")\n",
     "    print(f\"Connected to {COORDINODE_ADDR}\")\n",
     "else:\n",
     "    try:\n",
@@ -181,6 +184,9 @@
     "        from coordinode import CoordinodeClient\n",
     "\n",
     "        client = CoordinodeClient(COORDINODE_ADDR)\n",
+    "        if not client.health():\n",
+    "            client.close()\n",
+    "            raise RuntimeError(f\"CoordiNode at {COORDINODE_ADDR} is not serving health checks\")\n",
     "        print(f\"Connected to {COORDINODE_ADDR}\")\n",
     "    else:\n",
     "        # No server available — use the embedded in-process engine.\n",
@@ -196,7 +202,7 @@
     "\n",
     "        _lc = LocalClient(\":memory:\")\n",
     "        client = _EmbeddedAdapter(_lc)\n",
-    "        print(\"Using embedded LocalClient (in-process)\")"
+    "        print(\"Using embedded LocalClient (in-process)\")\n"
    ]
   },
   {

demo/notebooks/02_langchain_graph_chain.ipynb

@@ -99,7 +99,7 @@
     "        \"-q\",\n",
     "        \"coordinode\",\n",
     "        \"langchain\",\n",
-    "        \"langchain-coordinode\",\n",
+    "        \"git+https://github.com/structured-world/coordinode-python.git@4efc7b287211f4cfcf203ce92c83773d7d72ff61#subdirectory=langchain-coordinode\",\n",
     "        \"langchain-community\",\n",
     "        \"langchain-openai\",\n",
     "    ],\n",