splash screen (#8270)

# 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
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Include a link to a bug report or enhancement request.

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

@@ -184,6 +184,10 @@ fn gpt52_codex_upgrade() -> codex_protocol::openai_models::ModelUpgrade {
         reasoning_effort_mapping: None,
         migration_config_key: "gpt-5.2-codex".to_string(),
         model_link: Some("https://openai.com/index/introducing-gpt-5-2-codex".to_string()),
+        upgrade_copy: Some(
+            "Codex is now powered by gpt-5.2-codex, our latest frontier agentic coding model. It is smarter and faster than its predecessors and capable of long-running project-scale work."
+                .to_string(),
+        ),
     }
 }