Update models.json (#18586)

- Replace the active models-manager catalog with the deleted core
catalog contents.
- Replace stale hardcoded test model slugs with current bundled model
slugs.
- Keep this as a stacked change on top of the cleanup PR.

codex-rs/core/src/realtime_context_tests.rs

@@ -35,7 +35,7 @@ fn stored_thread(cwd: &str, title: &str, first_user_message: &str) -> StoredThre
         preview: first_user_message.to_string(),
         name: (!title.is_empty()).then(|| title.to_string()),
         model_provider: "test-provider".to_string(),
-        model: Some("gpt-5".to_string()),
+        model: Some("gpt-5.2".to_string()),
         reasoning_effort: None,
         created_at: Utc
             .timestamp_opt(1_709_251_100, 0)