fix: typos in model picker (#6859)

# External (non-OpenAI) Pull Request Requirements

Before opening this Pull Request, please read the dedicated
"Contributing" markdown file or your PR may be closed:
https://github.com/openai/codex/blob/main/docs/contributing.md

If your PR conforms to our contribution guidelines, replace this text
with a detailed and high quality description of your changes.

Include a link to a bug report or enhancement request.

codex-rs/core/tests/suite/client.rs

@@ -1155,7 +1155,7 @@ async fn token_count_includes_rate_limits_snapshot() {
                     "reasoning_output_tokens": 0,
                     "total_tokens": 123
                 },
-                // Default model is gpt-5.1-codex in tests → 95% usable context window
+                // Default model is arcticfox in tests → 95% usable context window
                 "model_context_window": 258400
             },
             "rate_limits": {

codex-rs/core/tests/suite/prompt_caching.rs

@@ -167,11 +167,12 @@ async fn prompt_tools_are_consistent_across_requests() -> anyhow::Result<()> {
                 "list_mcp_resource_templates",
                 "read_mcp_resource",
                 "update_plan",
+                "apply_patch",
                 "view_image",
             ],
         ),
         (
-            "gpt-5.1",
+            "arcticfox",
             vec![
                 "shell_command",
                 "list_mcp_resources",