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/main-wiring.test.ts

@@ -37,7 +37,6 @@ test('media path changes clear rendered subtitle state without clearing same-you
 
   assert.ok(actionBlock);
   assert.match(actionBlock, /appState\.currentSubText = '';/);
-  assert.match(actionBlock, /appState\.currentSubAssText = '';/);
   assert.match(actionBlock, /appState\.currentSubtitleData = null;/);
   assert.match(actionBlock, /isSameYoutubeMediaPath\(/);
   assert.match(actionBlock, /if \(!preserveParsedSubtitleCues\)/);