chore(docs): add note about context var handling (#8953)

Author: hntrl

docs/core_docs/docs/how_to/tool_runtime.ipynb

@@ -240,6 +240,17 @@
         "console.log(userToPets);"
       ]
     },
+    {
+      "cell_type": "markdown",
+      "metadata": {},
+      "source": [
+        "```{=mdx}\n",
+        ":::info Context Behavior\n",
+        "Context variables pinned using `setContextVariable`. This means that if the value is passed by reference, and the value is later reaccessed using `getContextVariable`, the changes will be reflected in the original value.\n",
+        ":::\n",
+        "```"
+      ]
+    },
     {
       "cell_type": "markdown",
       "metadata": {},