Persist model & reasoning changes (#2799)

Persists `/model` changes across both general and profile-specific
sessions.

codex-rs/core/src/lib.rs

@@ -16,6 +16,7 @@ mod codex_conversation;
 pub mod token_data;
 pub use codex_conversation::CodexConversation;
 pub mod config;
+pub mod config_edit;
 pub mod config_profile;
 pub mod config_types;
 mod conversation_history;