feat(overlay): forward mpv mouse and wheel bindings through overlay

- Accept WHEEL_UP/DOWN/LEFT/RIGHT (with modifiers) in keybindings, the plugin, and the settings key editor
- Forward mpv's MBTN_* and WHEEL_* bindings from the overlay so double-click fullscreen, wheel volume, and similar inputs work on Hyprland; SubMiner bindings and right-click pause still win
- Notify the overlay via mpv-input-bindings:changed when mpv's key set changes, fixing dead imported keys when the overlay loads before mpv connects
- Sync README requirements/quick start with the installation guide and fix the Arch MeCab install command (AUR mecab-git)

src/types/runtime.ts

@@ -656,6 +656,7 @@ export interface ElectronAPI {
   ) => void;
   reportOverlayContentBounds: (measurement: OverlayContentMeasurement) => void;
   onSessionBindingsChanged: (callback: (bindings: CompiledSessionBinding[]) => void) => void;
+  onMpvInputBindingsChanged: (callback: () => void) => void;
   onConfigHotReload: (callback: (payload: ConfigHotReloadPayload) => void) => void;
 }