## Summary
- exit shell mode when `Esc` is pressed while the absorbed `!` is the
only input
- add direct regression coverage plus a composer snapshot for the
restored normal prompt state
## Root cause
Shell mode stores the leading `!` outside the editable textarea. After
typing only `!`, the textarea is empty but the composer is still in bash
mode, so the existing empty-composer `Esc` handling never runs.
## Validation
- `just fmt`
- `cargo test -p codex-tui
bottom_pane::chat_composer::tests::esc_exits_empty_shell_mode`
- `cargo test -p codex-tui
bottom_pane::chat_composer::tests::footer_mode_snapshots`
- `cargo insta pending-snapshots`
`cargo test -p codex-tui` still reports unrelated existing `/status`
snapshot drift in this local environment because the rendered
permissions text is `workspace-write with network access` instead of the
older `read-only` fixture text.