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/core/services/index.ts

@@ -72,6 +72,10 @@ export {
   syncOverlayWindowLayer,
   updateOverlayWindowBounds,
 } from './overlay-window';
+export {
+  handleOverlayWindowBeforeInputEvent,
+  isTabInputForMpvForwarding,
+} from './overlay-window-input';
 export { initializeOverlayRuntime } from './overlay-runtime-init';
 export { setVisibleOverlayVisible, updateVisibleOverlayVisibility } from './overlay-visibility';
 export {