fix: remove existing process hardening from Codex CLI (#8951)

As explained in https://github.com/openai/codex/issues/8945 and
https://github.com/openai/codex/issues/8472, there are legitimate cases
where users expect processes spawned by Codex to inherit environment
variables such as `LD_LIBRARY_PATH` and `DYLD_LIBRARY_PATH`, where
failing to do so can cause significant performance issues.

This PR removes the use of
`codex_process_hardening::pre_main_hardening()` in Codex CLI (which was
added not in response to a known security issue, but because it seemed
like a prudent thing to do from a security perspective:
https://github.com/openai/codex/pull/4521), but we will continue to use
it in `codex-responses-api-proxy`. At some point, we probably want to
introduce a slightly different version of
`codex_process_hardening::pre_main_hardening()` in Codex CLI that
excludes said environment variables from the Codex process itself, but
continues to propagate them to subprocesses.

codex-rs/cli/src/main.rs

@@ -418,14 +418,6 @@ fn stage_str(stage: codex_core::features::Stage) -> &'static str {
     }
 }
 
-/// As early as possible in the process lifecycle, apply hardening measures. We
-/// skip this in debug builds to avoid interfering with debugging.
-#[ctor::ctor]
-#[cfg(not(debug_assertions))]
-fn pre_main_hardening() {
-    codex_process_hardening::pre_main_hardening();
-}
-
 fn main() -> anyhow::Result<()> {
     arg0_dispatch_or_else(|codex_linux_sandbox_exe| async move {
         cli_main(codex_linux_sandbox_exe).await?;