Introduce Offset type to track scroll positions and replace
ScrollbarState fields in SkirmishState
Update keybindings, App::draw, Widget impl, and BoardWidget::new
to use mutable references and the new Offset struct.
Adjust imports accordingly.
Introduce directional and scroll actions, update keybindings, add
scrollbar
state to SkirmishState, and render the board with a new BoardWidget.
Adjust CLI
defaults and layout heights accordingly.
Removed the settings UI and its keybinding logic, added a skirmish view
and corresponding keybindings, simplified the SettingsState to hold
skirmish configuration, updated module exports, and changed the CLI
default map height from 25 to 21. Also fixed the main menu selection
limit.