Remove config lockfile support (#38011)

## What changed

- Remove effective-config lockfile export, replay, and validation from session startup.
- Remove the `debug.config_lockfile` settings and generated schema entries.
- Remove feature-config materialization helpers that were only used to create lockfiles.

GitOrigin-RevId: a8c07c1c06325b3ec3dae9a97c36c2488d37df25

codex-rs/core/src/lib.rs

@@ -25,7 +25,6 @@ mod compact_remote;
 mod compact_remote_history;
 mod compact_remote_v2;
 mod compact_token_budget;
-mod config_lock;
 mod user_message_admission;
 pub use codex_thread::BackgroundTerminalInfo;
 pub use codex_thread::CodexThread;