Add XMonad.Hooks.Modal to separate layout switching and master pane
manipulation into distinct modal namespaces. This resolves keybinding
conflicts and creates a more organized interaction model.
Changes:
- Layout mode (M-a l): one-shot layout selection (d/m/f)
- Master mode (M-a m): persistent pane adjustments with arrow keys
- Restore ppExtras with logMode to display active mode in xmobar
- Remove conflicting Home/End/PageUp/PageDown bindings from master pane
- Simplify navigation by moving screen focus back to Home/End
