refactor(ipc): remove dead preload methods and the ASS line broadcast (#293)

Drop 16 overlay preload methods with no caller (onSubtitleAss,
getCurrentSubtitleAss, onVisibility, getOverlayVisibility,
openYomitanSettings, quitApp, toggleOverlay, getMecabStatus,
setMecabEnabled, getKeybindings, saveControllerPreference,
getAnkiConnectStatus, setAnkiConnectEnabled, clearAnkiConnectHistory,
cycleRuntimeOption, appendClipboardVideoToQueue) along with their
IPC_CHANNELS keys, handlers, validators and dep plumbing.

With both ASS consumers gone, stop observing sub-text/ass in mpv and
remove the subtitle-ass-change event chain and appState.currentSubAssText.
The main-process functions these wrapped stay; tray, CLI, shortcuts and
session actions still use them.

src/main/state.ts

@@ -160,7 +160,6 @@ export interface AppState {
   discordPresenceService: ReturnType<typeof createDiscordPresenceService> | null;
   reconnectTimer: ReturnType<typeof setTimeout> | null;
   currentSubText: string;
-  currentSubAssText: string;
   currentSubtitleData: SubtitleData | null;
   activeParsedSubtitleCues: SubtitleCue[];
   activeParsedSubtitleSource: string | null;
@@ -247,7 +246,6 @@ export function createAppState(values: AppStateInitialValues): AppState {
     discordPresenceService: null,
     reconnectTimer: null,
     currentSubText: '',
-    currentSubAssText: '',
     currentSubtitleData: null,
     activeParsedSubtitleCues: [],
     activeParsedSubtitleSource: null,