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/tests/suite/tool_harness.rs

@@ -51,7 +51,7 @@ async fn shell_tool_executes_command_and_streams_output() -> anyhow::Result<()>
 
     let server = start_mock_server().await;
 
-    let mut builder = test_codex().with_model("gpt-5");
+    let mut builder = test_codex().with_model("test-local-shell-json");
     let TestCodex {
         codex,
         cwd,