bug: sandbox denied error logs (#4874)

Check on STDOUT / STDERR or aggregated output for some logs when sanbox
is denied

codex-rs/core/src/executor/runner.rs

@@ -380,6 +380,23 @@ mod tests {
         assert_eq!(message, "failed in sandbox: sandbox stderr");
     }
 
+    #[test]
+    fn sandbox_failure_message_falls_back_to_aggregated_output() {
+        let output = ExecToolCallOutput {
+            exit_code: 101,
+            stdout: StreamOutput::new(String::new()),
+            stderr: StreamOutput::new(String::new()),
+            aggregated_output: StreamOutput::new("aggregate text".to_string()),
+            duration: Duration::from_millis(10),
+            timed_out: false,
+        };
+        let err = SandboxErr::Denied {
+            output: Box::new(output),
+        };
+        let message = sandbox_failure_message(err);
+        assert_eq!(message, "failed in sandbox: aggregate text");
+    }
+
     #[test]
     fn normalize_function_error_synthesizes_payload() {
         let err = FunctionCallError::RespondToModel("boom".to_string());