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/core/services/mpv-protocol.test.ts

@@ -59,7 +59,6 @@ function createDeps(overrides: Partial<MpvProtocolHandleMessageDeps> = {}): {
       getSubtitleMetrics: () => metrics,
       isVisibleOverlayVisible: () => false,
       emitSubtitleChange: (payload) => state.events.push(payload),
-      emitSubtitleAssChange: (payload) => state.events.push(payload),
       emitSubtitleTiming: (payload) => state.events.push(payload),
       emitSecondarySubtitleChange: (payload) => state.events.push(payload),
       emitSubtitleTrackChange: (payload) => state.events.push(payload),
@@ -132,28 +131,6 @@ test('dispatchMpvProtocolMessage emits subtitle text on property change', async
   assert.deepEqual(state.events, [{ text: '字幕', isOverlayVisible: false }]);
 });
 
-test('dispatchMpvProtocolMessage emits ASS subtitle text from the current mpv property', async () => {
-  const { deps, state } = createDeps();
-
-  await dispatchMpvProtocolMessage(
-    { event: 'property-change', name: 'sub-text/ass', data: '{\\b1}字幕' },
-    deps,
-  );
-
-  assert.deepEqual(state.events, [{ text: '{\\b1}字幕' }]);
-});
-
-test('dispatchMpvProtocolMessage emits ASS subtitle text from the legacy mpv property', async () => {
-  const { deps, state } = createDeps();
-
-  await dispatchMpvProtocolMessage(
-    { event: 'property-change', name: 'sub-text-ass', data: '{\\b1}字幕' },
-    deps,
-  );
-
-  assert.deepEqual(state.events, [{ text: '{\\b1}字幕' }]);
-});
-
 test('dispatchMpvProtocolMessage emits subtitle track changes', async () => {
   const { deps, state } = createDeps({
     emitSubtitleTrackChange: (payload) => state.events.push(payload),