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/tasks/mod_tests.rs

@@ -25,8 +25,8 @@ fn test_session_telemetry() -> SessionTelemetry {
     .expect("in-memory metrics client");
     SessionTelemetry::new(
         ThreadId::new(),
-        "gpt-5.1",
-        "gpt-5.1",
+        "gpt-5.4",
+        "gpt-5.4",
         /*account_id*/ None,
         /*account_email*/ None,
         /*auth_mode*/ None,