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/shared/ipc/validators.ts

@@ -10,7 +10,6 @@ import type {
 } from '../../types/integrations';
 import type {
   ControllerConfigUpdate,
-  ControllerPreferenceUpdate,
   SessionActionDispatchRequest,
   SubsyncManualRunRequest,
 } from '../../types/runtime';
@@ -131,16 +130,6 @@ export function parseSubtitlePosition(value: unknown): SubtitlePosition | null {
   };
 }
 
-export function parseControllerPreferenceUpdate(value: unknown): ControllerPreferenceUpdate | null {
-  if (!isObject(value)) return null;
-  if (typeof value.preferredGamepadId !== 'string') return null;
-  if (typeof value.preferredGamepadLabel !== 'string') return null;
-  return {
-    preferredGamepadId: value.preferredGamepadId,
-    preferredGamepadLabel: value.preferredGamepadLabel,
-  };
-}
-
 function parseDiscreteBinding(value: unknown) {
   if (!isObject(value) || typeof value.kind !== 'string') return null;
   if (value.kind === 'none') {
@@ -328,10 +317,6 @@ export function parseRuntimeOptionId(value: unknown): RuntimeOptionId | null {
   return RUNTIME_OPTION_IDS.includes(value as RuntimeOptionId) ? (value as RuntimeOptionId) : null;
 }
 
-export function parseRuntimeOptionDirection(value: unknown): 1 | -1 | null {
-  return value === 1 || value === -1 ? value : null;
-}
-
 export function parseRuntimeOptionValue(value: unknown): RuntimeOptionValue | null {
   return typeof value === 'boolean' || typeof value === 'string'
     ? (value as RuntimeOptionValue)