feat: update default (#4076)

Changes:
- Default model and docs now use gpt-5-codex. 
- Disables the GPT-5 Codex NUX by default.
- Keeps presets available for API key users.

codex-rs/core/src/config.rs

@@ -37,7 +37,7 @@ use toml_edit::DocumentMut;
 use toml_edit::Item as TomlItem;
 use toml_edit::Table as TomlTable;
 
-const OPENAI_DEFAULT_MODEL: &str = "gpt-5";
+const OPENAI_DEFAULT_MODEL: &str = "gpt-5-codex";
 const OPENAI_DEFAULT_REVIEW_MODEL: &str = "gpt-5-codex";
 pub const GPT_5_CODEX_MEDIUM_MODEL: &str = "gpt-5-codex";
 
@@ -54,7 +54,7 @@ pub struct Config {
     /// Optional override of model selection.
     pub model: String,
 
-    /// Model used specifically for review sessions. Defaults to "gpt-5".
+    /// Model used specifically for review sessions. Defaults to "gpt-5-codex".
     pub review_model: String,
 
     pub model_family: ModelFamily,
@@ -1366,7 +1366,7 @@ startup_timeout_ms = 2500
         tokio::fs::write(
             &config_path,
             r#"
-model = "gpt-5"
+model = "gpt-5-codex"
 model_reasoning_effort = "medium"
 
 [profiles.dev]
@@ -1441,7 +1441,7 @@ model = "gpt-4"
 model_reasoning_effort = "medium"
 
 [profiles.prod]
-model = "gpt-5"
+model = "gpt-5-codex"
 "#,
         )
         .await?;
@@ -1472,7 +1472,7 @@ model = "gpt-5"
                 .profiles
                 .get("prod")
                 .and_then(|profile| profile.model.as_deref()),
-            Some("gpt-5"),
+            Some("gpt-5-codex"),
         );
 
         Ok(())