feat(stats): add Hide Kana filter and fix vocabulary exclusion matching

- Remove overlay mining image toast; OSD card notifications no longer flash a frame screenshot
- Add Hide Kana toggle to frequency rank table to filter kana-only headwords
- Fix vocab exclusions to deduplicate and match token variants (e.g. ない / 無い) under one exclusion entry
- Skip cover image fetching when the overview tab is inactive

src/preload-settings.test.ts

@@ -34,13 +34,10 @@ test('overlay preload buffers only latest subtitle state until renderer listener
   assert.match(source, /onSubtitle:\s*\(callback:[\s\S]+?onSubtitleSetEvent\(callback\);/);
 });
 
-test('overlay preload buffers only latest mining image payload before listener registration', () => {
+test('overlay preload does not expose the old mining image toast IPC path', () => {
   const source = fs.readFileSync(path.join(process.cwd(), 'src', 'preload.ts'), 'utf8');
 
-  assert.match(
-    source,
-    /const onMiningImageEvent =\s*createLatestValueIpcListenerWithPayload<MiningImagePayload>\(\s*IPC_CHANNELS\.event\.miningImage,/,
-  );
+  assert.doesNotMatch(source, /MiningImagePayload|onMiningImage|IPC_CHANNELS\.event\.miningImage/);
 });
 
 test('overlay preload exposes queued pointer recovery requests', () => {