fix: update CLI usage order for codex -h (#5356)

Set clap usage override so help lists subcommands before the prompt
argument.

Author: tibo-openai

codex-rs/cli/src/main.rs

@@ -42,7 +42,8 @@ use codex_core::config::ConfigOverrides;
     // The executable is sometimes invoked via a platform‑specific name like
     // `codex-x86_64-unknown-linux-musl`, but the help output should always use
     // the generic `codex` command name that users run.
-    bin_name = "codex"
+    bin_name = "codex",
+    override_usage = "codex [OPTIONS] [PROMPT]\n       codex [OPTIONS] <COMMAND> [ARGS]"
 )]
 struct MultitoolCli {
     #[clap(flatten)]