feat(subtitles): add local Japanese subtitle generation

- Generate Japanese SRTs through the overlay modal or launcher
- Support managed whisper.cpp models and optional dialogue detection

src/renderer/modals/session-help-sections.ts

@@ -225,6 +225,8 @@ function describeSessionAction(
       return 'Open jimaku';
     case 'openTsukihime':
       return 'Open TsukiHime';
+    case 'openSubtitleGeneration':
+      return 'Generate Japanese subtitles';
     case 'openYoutubePicker':
       return 'Open YouTube subtitle picker';
     case 'openPlaylistBrowser':
@@ -266,6 +268,7 @@ function sectionForSessionBinding(binding: CompiledSessionBinding): string {
     case 'openJimaku':
     case 'openTsukihime':
     case 'openCharacterDictionaryManager':
+    case 'openSubtitleGeneration':
     case 'openControllerSelect':
     case 'openControllerDebug':
     case 'openYoutubePicker':