Related to https://github.com/openai/codex/pull/2848, I don't see the
stderr from `codex mcp` colocated with the other stderr from
`test_shell_command_approval_triggers_elicitation()` when it fails even
though we have `RUST_LOG=debug` set when we spawn `codex mcp`:
1e9e703b96/codex-rs/mcp-server/tests/common/mcp_process.rs (L65)
Let's try this new logic which should be more explicit.