CLUI Command bar and Search

The updated interface introduces a new command bar to balance discoverability with visual clutter, replacing old shortcuts and file switcher modal. The command bar allows for keyboard-centric interaction while providing an accessible way for beginners to learn about features. A search feature has been added, enabling users to index contents of files, see query results across every file, and navigate directly to specific lines in the code. Keyboard shortcuts are available, but a dedicated button or prefilled command may be introduced in the future to improve discoverability.