feat(config): unify mpv plugin options under main config and add CSS/Ani

- Replace subminer.conf plugin config with mpv.* fields in config.jsonc
- Add socketPath, backend, autoStartSubMiner, pauseUntilOverlayReady, aniskipEnabled/buttonKey, subminerBinaryPath to mpv config
- Add subtitleSidebar.css field; migrate legacy sidebar appearance fields
- Add paintOrder and WebkitTextStroke to subtitle style options
- Update default subtitle/sidebar fontFamily to CJK-first stack
- Fix overlay visible state surviving mpv y-r restart
- Fix live config saves applying subtitle CSS immediately to open overlays
- Migrate legacy primary/secondary subtitle appearance into subtitleStyle.css on load
- Switch AniSkip button key setting to click-to-learn key capture

src/main/runtime/config-settings-save.ts

@@ -24,6 +24,7 @@ export interface ConfigSettingsSaveDeps {
   reloadConfigStrict(): ReloadConfigStrictResult;
   classifyDiff(prev: ResolvedConfig, next: ResolvedConfig): ConfigSettingsHotReloadDiff;
   getRestartRequiredSections(restartRequiredFields: string[]): string[];
+  onHotReloadApplied?: (diff: ConfigSettingsHotReloadDiff, config: ResolvedConfig) => void;
 }
 
 export function createSaveConfigSettingsPatchHandler(deps: ConfigSettingsSaveDeps) {
@@ -86,6 +87,9 @@ export function createSaveConfigSettingsPatchHandler(deps: ConfigSettingsSaveDep
     }
 
     const diff = deps.classifyDiff(previousConfig, reloadResult.config);
+    if (diff.hotReloadFields.length > 0) {
+      deps.onHotReloadApplied?.(diff, reloadResult.config);
+    }
 
     return {
       ok: true,