Units that cannot be executed are shown in red on both the Units and
Plans tabs. Validation checks target existence/executability, shell
definition lookup, working directory existence, rectifier
existence/executability, and environment file existence.
The unit properties dialog applies live validation with GTK error
styling on each field and reports issues to the status bar as the
user edits. Selecting a unit or task re-runs validation so the
status bar always reflects the selected item.
Also separates plan dirty state from unit editor dirty state so
editing unit properties no longer marks the plan as unsaved.
- 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
