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/overlay-window-input.ts

@@ -0,0 +1,61 @@
+export type OverlayWindowKind = 'visible' | 'modal';
+
+export function isTabInputForMpvForwarding(input: Electron.Input): boolean {
+  if (input.type !== 'keyDown' || input.isAutoRepeat) return false;
+  if (input.alt || input.control || input.meta || input.shift) return false;
+  return input.code === 'Tab' || input.key === 'Tab';
+}
+
+function isLookupWindowToggleInput(input: Electron.Input): boolean {
+  if (input.type !== 'keyDown') return false;
+  if (input.alt) return false;
+  if (!input.control && !input.meta) return false;
+  if (input.shift) return false;
+  const normalizedKey = typeof input.key === 'string' ? input.key.toLowerCase() : '';
+  return input.code === 'KeyY' || normalizedKey === 'y';
+}
+
+function isKeyboardModeToggleInput(input: Electron.Input): boolean {
+  if (input.type !== 'keyDown') return false;
+  if (input.alt) return false;
+  if (!input.control && !input.meta) return false;
+  if (!input.shift) return false;
+  const normalizedKey = typeof input.key === 'string' ? input.key.toLowerCase() : '';
+  return input.code === 'KeyY' || normalizedKey === 'y';
+}
+
+export function handleOverlayWindowBeforeInputEvent(options: {
+  kind: OverlayWindowKind;
+  windowVisible: boolean;
+  input: Electron.Input;
+  preventDefault: () => void;
+  sendKeyboardModeToggleRequested: () => void;
+  sendLookupWindowToggleRequested: () => void;
+  tryHandleOverlayShortcutLocalFallback: (input: Electron.Input) => boolean;
+  forwardTabToMpv: () => void;
+}): boolean {
+  if (options.kind === 'modal') return false;
+  if (!options.windowVisible) return false;
+
+  if (isKeyboardModeToggleInput(options.input)) {
+    options.preventDefault();
+    options.sendKeyboardModeToggleRequested();
+    return true;
+  }
+
+  if (isLookupWindowToggleInput(options.input)) {
+    options.preventDefault();
+    options.sendLookupWindowToggleRequested();
+    return true;
+  }
+
+  if (isTabInputForMpvForwarding(options.input)) {
+    options.preventDefault();
+    options.forwardTabToMpv();
+    return true;
+  }
+
+  if (!options.tryHandleOverlayShortcutLocalFallback(options.input)) return false;
+  options.preventDefault();
+  return true;
+}