Improve startup dictionary progress and fix overlay/plugin input handlin

- show a dedicated startup OSD "building" phase for character dictionary sync
- forward bare `Tab` from visible overlay to mpv so AniSkip works while focused
- fix Windows plugin env override resolution for `SUBMINER_BINARY_PATH`

src/main/runtime/startup-osd-sequencer.ts

@@ -1,5 +1,5 @@
 export interface StartupOsdSequencerCharacterDictionaryEvent {
-  phase: 'checking' | 'generating' | 'syncing' | 'importing' | 'ready' | 'failed';
+  phase: 'checking' | 'generating' | 'syncing' | 'building' | 'importing' | 'ready' | 'failed';
   message: string;
 }
 
@@ -74,6 +74,7 @@ export function createStartupOsdSequencer(deps: { showOsd: (message: string) =>
         event.phase === 'checking' ||
         event.phase === 'generating' ||
         event.phase === 'syncing' ||
+        event.phase === 'building' ||
         event.phase === 'importing'
       ) {
         pendingDictionaryProgress = event;