- Reorder tabs: Rex Config, Units, Plans, Shells
- Beautify Units, Plans, Shells, and Config tabs with framed lists,
linked button groups, consistent margins, and dim labels
- Grey out plan controls and task properties when no plan/task loaded
- Restructure shells from single-file to multi-file directory model,
paralleling the units architecture (create/delete/save files,
create/delete/edit/move shells within files)
- Fix shells loading to scan directories for .shells files
- Beautify unit properties dialog with GtkFrame sections, dim-label
field labels, internal padding, and linked file action buttons
- Add rectifier Select/Open/Create file buttons
- Fix GtkSwitch multi-click issue using state-set signal
- Move Save File button to unit files sidebar
- Sync unit editor state after name changes in properties dialog
