Convert memory_manager cells to markdown in 02_role_of_context_engine

Cells that used the non-existent memory_manager are now markdown
cells with code examples. This allows the notebook to run without
errors while still demonstrating the concepts.

The actual memory implementation is shown in Section 3 notebooks.

Author: abrookins

python-recipes/context-engineering/notebooks/section-1-introduction/02_role_of_context_engine.ipynb

@@ -474,11 +474,14 @@
       ]
     },
     {
-      "cell_type": "code",
+      "cell_type": "markdown",
       "execution_count": null,
       "metadata": {},
       "outputs": [],
       "source": [
+        "**Conceptual Example (not executable in this notebook)**\n",
+        "\n",
+        "```python\n",
         "import time\n",
         "import asyncio\n",
         "\n",
@@ -547,7 +550,10 @@
         "if redis_config.health_check():\n",
         "    await benchmark_context_engine()\n",
         "else:\n",
-        "    print(\"\u274c Redis not available for performance testing\")"
+        "    print(\"\u274c Redis not available for performance testing\")",
+        "```\n",
+        "\n",
+        "*Note: This demonstrates the concept. See Section 3 notebooks for actual memory implementation using MemoryClient.*\n"
       ]
     },
     {
@@ -630,11 +636,14 @@
       ]
     },
     {
-      "cell_type": "code",
+      "cell_type": "markdown",
       "execution_count": null,
       "metadata": {},
       "outputs": [],
       "source": [
+        "**Conceptual Example (not executable in this notebook)**\n",
+        "\n",
+        "```python\n",
         "# Real-world scenario demonstration\n",
         "print(\"\ud83c\udf0d Real-World Context Engine Scenario\")\n",
         "print(\"=\" * 50)\n",
@@ -758,7 +767,10 @@
         "if redis_config.health_check():\n",
         "    await realistic_scenario()\n",
         "else:\n",
-        "    print(\"\u274c Redis not available for scenario demonstration\")"
+        "    print(\"\u274c Redis not available for scenario demonstration\")",
+        "```\n",
+        "\n",
+        "*Note: This demonstrates the concept. See Section 3 notebooks for actual memory implementation using MemoryClient.*\n"
       ]
     },
     {