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/runtime-options-ipc.test.ts

@@ -2,7 +2,6 @@ import test from 'node:test';
 import assert from 'node:assert/strict';
 import {
   applyRuntimeOptionResultRuntime,
-  cycleRuntimeOptionFromIpcRuntime,
   setRuntimeOptionFromIpcRuntime,
 } from './runtime-options-ipc';
 
@@ -25,21 +24,3 @@ test('setRuntimeOptionFromIpcRuntime returns unavailable when manager missing',
   assert.equal(result.error, 'Runtime options manager unavailable');
   assert.deepEqual(osd, []);
 });
-
-test('cycleRuntimeOptionFromIpcRuntime reports errors once', () => {
-  const osd: string[] = [];
-  const result = cycleRuntimeOptionFromIpcRuntime(
-    {
-      setOptionValue: () => ({ ok: true }),
-      cycleOption: () => ({ ok: false, error: 'bad option' }),
-    },
-    'anki.kikuFieldGrouping',
-    1,
-    (text) => {
-      osd.push(text);
-    },
-  );
-  assert.equal(result.ok, false);
-  assert.equal(result.error, 'bad option');
-  assert.deepEqual(osd, ['bad option']);
-});