Fast keyboard-driven ISO routing for operators with one hand on the keyboard during a show. Both NumPad1..9 and top-row 1..9 bind to ToggleByIndexCommand which resolves against the filtered+sorted ParticipantsView — index matches what's on screen, not the underlying storage order.
Press a digit again to toggle off. Plays nice with sort modes: LoudestFirst means '1' is always whoever's loudest right now; Alphabetical lets you build muscle memory for recurring guests.
Implementation:
- New generic RelayCommand<T> in RelayCommand.cs so XAML CommandParameter strings convert to the action's T (int / string / etc.).
- ToggleByIndexCommand on MainViewModel iterates ParticipantsView, finds the Nth ParticipantViewModel, fires its ToggleIsoCommand if CanExecute.
- 18 KeyBindings (9 NumPad + 9 D1-D9) in MainWindow.xaml's Window.InputBindings.
- F1 help cheat sheet updated to mention the new range.
