## Summary
- Reverts PR #17749 so queued inter-agent mail can again preempt after
reasoning/commentary output item boundaries.
- Applies the revert to the current `codex/turn.rs` module layout and
restores the prior pending-input test expectations/snapshots.
## Testing
- `just fmt`
- `cargo test -p codex-core --test all pending_input`
- `cargo test -p codex-core` failed in unrelated
`tools::js_repl::tests::js_repl_imported_local_files_can_access_repl_globals`:
dotslash download hit `mktemp: mkdtemp failed ... Operation not
permitted` in the sandbox temp dir.
Co-authored-by: Codex <noreply@openai.com>
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