feat: detach non-tty childs (#9477)

Thanks to the investigations made by
* @frantic-openai https://github.com/openai/codex/pull/9403
* @kfiramar https://github.com/openai/codex/pull/9388

codex-rs/core/src/shell_snapshot.rs

@@ -135,6 +135,13 @@ async fn run_shell_script_with_timeout(
     // returns a ref of handler.
     let mut handler = Command::new(&args[0]);
     handler.args(&args[1..]);
+    #[cfg(unix)]
+    unsafe {
+        handler.pre_exec(|| {
+            codex_utils_pty::process_group::detach_from_tty()?;
+            Ok(())
+        });
+    }
     handler.kill_on_drop(true);
     let output = timeout(snapshot_timeout, handler.output())
         .await

codex-rs/core/src/spawn.rs

@@ -66,12 +66,12 @@ pub(crate) async fn spawn_child_async(
 
     #[cfg(unix)]
     unsafe {
-        let set_process_group = matches!(stdio_policy, StdioPolicy::RedirectForShellTool);
+        let detach_from_tty = matches!(stdio_policy, StdioPolicy::RedirectForShellTool);
         #[cfg(target_os = "linux")]
         let parent_pid = libc::getpid();
         cmd.pre_exec(move || {
-            if set_process_group {
-                codex_utils_pty::process_group::set_process_group()?;
+            if detach_from_tty {
+                codex_utils_pty::process_group::detach_from_tty()?;
             }
 
             // This relies on prctl(2), so it only works on Linux.