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

stats/src/components/vocabulary/FrequencyRankTable.test.tsx

@@ -1,7 +1,11 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
 import { renderToStaticMarkup } from 'react-dom/server';
-import { FrequencyRankTable } from './FrequencyRankTable';
+import {
+  buildFrequencyRankRows,
+  FrequencyRankTable,
+  isKanaOnlyTokenText,
+} from './FrequencyRankTable';
 import type { VocabularyEntry } from '../../types/stats';
 
 function makeEntry(over: Partial<VocabularyEntry>): VocabularyEntry {
@@ -41,3 +45,42 @@ test('omits reading when reading equals headword', () => {
     'should not render any bracketed reading when equal to headword',
   );
 });
+
+test('identifies kana-only token text without hiding mixed kanji words', () => {
+  assert.equal(isKanaOnlyTokenText('さらに'), true);
+  assert.equal(isKanaOnlyTokenText('バカ'), true);
+  assert.equal(isKanaOnlyTokenText('カレー'), true);
+  assert.equal(isKanaOnlyTokenText('前に'), false);
+  assert.equal(isKanaOnlyTokenText('間違いない'), false);
+});
+
+test('frequency rows can hide kana-only headwords', () => {
+  const rows = buildFrequencyRankRows(
+    [
+      makeEntry({ wordId: 1, headword: 'さらに', word: 'さらに', frequencyRank: 10 }),
+      makeEntry({
+        wordId: 2,
+        headword: '前に',
+        word: '前に',
+        reading: 'まえに',
+        frequencyRank: 20,
+      }),
+      makeEntry({ wordId: 3, headword: 'バカ', word: 'バカ', reading: 'バカ', frequencyRank: 30 }),
+    ],
+    new Set(),
+    { hideKnown: false, hideKanaOnly: true },
+  );
+
+  assert.deepEqual(
+    rows.map((row) => row.headword),
+    ['前に'],
+  );
+});
+
+test('renders a Hide Kana filter button', () => {
+  const entry = makeEntry({ headword: 'さらに', word: 'さらに', reading: 'さらに' });
+  const markup = renderToStaticMarkup(
+    <FrequencyRankTable words={[entry]} knownWords={new Set()} />,
+  );
+  assert.match(markup, /Hide Kana/);
+});