Replace the single `mode` option with separate `keyboard_focus_animation`
and `mouse_focus_animation` settings, leveraging `Desktop::eFocusReason`
to distinguish focus source. This allows different effects (or none) for
keyboard vs mouse focus changes.
New config options:
- `enable` — toggle the plugin on/off
- `animate_floating` — control whether floating windows animate
- `keyboard_focus_animation` — animation for keyboard focus (default: flash)
- `mouse_focus_animation` — animation for mouse focus (default: none)
Renamed `bounce` → `shrink` and `bounce_strength` → `shrink_percentage`
for clarity. Preserves existing `only_on_monitor_change`, `fade_opacity`,
and `slide_height` options.
