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/preload.ts

@@ -662,6 +662,9 @@ const electronAPI: ElectronAPI = {
       (_event, bindings: import('./types').CompiledSessionBinding[]) => callback(bindings),
     );
   },
+  onMpvInputBindingsChanged: (callback: () => void) => {
+    ipcRenderer.on(IPC_CHANNELS.event.mpvInputBindingsChanged, () => callback());
+  },
   onConfigHotReload: (callback: (payload: ConfigHotReloadPayload) => void) => {
     ipcRenderer.on(
       IPC_CHANNELS.event.configHotReload,