Add conceptual docs on accessing HttpContext (#771)

* Add doc with sample on accessing HttpContext
* Apply suggestions from PR review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

docs/concepts/httpcontext/samples/TryItOut.ipynb

@@ -0,0 +1,112 @@
+{
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+    },
+    "polyglot_notebook": {
+     "kernelName": "csharp"
+    }
+   },
+   "source": [
+    "## HTTP Context\n",
+    "\n",
+    "This project illustrates how to access the HttpContext from tool calls. See the [README](../README.md) for more details.\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "093a7d4f",
+   "metadata": {},
+   "source": [
+    "### Examples\n",
+    "\n",
+    "The following request illustrates a tool call that retrieves the HTTP headers from the [HttpContext] using the [IHttpContextAccessor].\n",
+    "\n",
+    "The server implements two other tools, `get_request_info` and `get_user_claims`. You can modify the code below to call these tools as well,\n",
+    "which illustrate how to access other parts of the [HttpContext].\n",
+    "\n",
+    "\n",
+    "[HttpContext]: https://docs.microsoft.com/dotnet/api/microsoft.aspnetcore.http.httpcontext\n",
+    "[IHttpContextAccessor]: https://docs.microsoft.com/dotnet/api/microsoft.aspnetcore.http.ihttpcontextaccessor"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "id": "3324ec56",
+   "metadata": {
+    "language_info": {
+     "name": "polyglot-notebook"
+    },
+    "polyglot_notebook": {
+     "kernelName": "pwsh"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "{\n",
+      "  \"result\": {\n",
+      "    \"content\": [\n",
+      "      {\n",
+      "        \"type\": \"text\",\n",
+      "        \"text\": \"[]\"\n",
+      "      }\n",
+      "    ],\n",
+      "    \"structuredContent\": {\n",
+      "      \"result\": []\n",
+      "    }\n",
+      "  },\n",
+      "  \"id\": 1,\n",
+      "  \"jsonrpc\": \"2.0\"\n",
+      "}\n"
+     ]
+    }
+   ],
+   "source": [
+    "curl -s -X POST http://localhost:3001 `\n",
+    "-H \"ProtocolVersion: 2025-06-18\" `\n",
+    "-H \"Accept: application/json, text/event-stream\" `\n",
+    "-H \"Content-Type: application/json\" `\n",
+    "-d '{\n",
+    "    \"jsonrpc\": \"2.0\",\n",
+    "    \"id\": 1,\n",
+    "    \"method\": \"tools/call\",\n",
+    "    \"params\": {\n",
+    "        \"name\": \"get_user_claims\"\n",
+    "    }\n",
+    "}' | Where-Object { $_ -like \"data:*\" } | ForEach-Object { $_.Substring(5) } | jq"
+   ]
+  }
+ ],
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+   "language": "C#",
+   "name": ".net-csharp"
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+   "name": "polyglot-notebook"
+  },
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+ "nbformat_minor": 5
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