- Introduce built‑in Emacs keymap (`keymap_emacs.toml`) alongside existing Vim layout.
- Add `ui.keymap_profile` and `ui.keymap_path` configuration options; persist profile changes via `:keymap` command.
- Expose `KeymapProfile` enum (Vim, Emacs, Custom) and integrate it throughout state, UI rendering, and help overlay.
- Extend command registry with `keymap.set_vim` and `keymap.set_emacs` to allow profile switching.
- Update help overlay, command specs, and README to reflect new keybindings and profile commands.
- Adjust `Keymap::load` to honor preferred profile, custom paths, and fallback logic.
