## Summary
- show a dim “(no output)” placeholder when an executed command produces
no stdout or stderr so empty runs are visible
- update TUI snapshots to include the new placeholder in history
renderings
## Testing
- cargo test -p codex-tui
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https://chatgpt.com/codex/tasks/task_i_68dc056c1d5883218fe8d9929e9b1657
- Refactor Exec Cell into its own module
- update exec command rendering to inline the first command line
- limit continuation lines
- always show trimmed output