fix(overlay): remove content adverbs from annotation stop-word list

- 確かに and やはり no longer excluded from frequency/JLPT highlighting and vocab stats
- Stop-word list now covers only interjections, pronouns, and grammar fragments

src/core/services/tokenizer/annotation-stage.test.ts

@@ -728,15 +728,6 @@ test('shouldExcludeTokenFromVocabularyPersistence excludes common frequency stop
       pos2: '代名詞|副助詞／並立助詞／終助詞',
       pos3: '一般|*',
     }),
-    makeToken({
-      surface: '確かに',
-      headword: '確かに',
-      reading: 'たしかに',
-      partOfSpeech: PartOfSpeech.other,
-      pos1: '名詞|助詞',
-      pos2: '形容動詞語幹|副詞化',
-      pos3: '*',
-    }),
     makeToken({
       surface: 'あなた',
       headword: '貴方',
@@ -753,6 +744,34 @@ test('shouldExcludeTokenFromVocabularyPersistence excludes common frequency stop
   }
 });
 
+test('content adverbs are not excluded from annotations or vocabulary persistence', () => {
+  const tokens = [
+    makeToken({
+      surface: '確かに',
+      headword: '確かに',
+      reading: 'たしかに',
+      partOfSpeech: PartOfSpeech.other,
+      pos1: '名詞|助詞',
+      pos2: '形容動詞語幹|副詞化',
+      pos3: '*',
+    }),
+    makeToken({
+      surface: 'やはり',
+      headword: 'やはり',
+      reading: 'ヤハリ',
+      partOfSpeech: PartOfSpeech.other,
+      pos1: '副詞',
+      pos2: '一般',
+      pos3: '*',
+    }),
+  ];
+
+  for (const token of tokens) {
+    assert.equal(shouldExcludeTokenFromSubtitleAnnotations(token), false, token.surface);
+    assert.equal(shouldExcludeTokenFromVocabularyPersistence(token), false, token.surface);
+  }
+});
+
 test('shouldExcludeTokenFromSubtitleAnnotations excludes standalone して grammar helper fragments', () => {
   const token = makeToken({
     surface: 'して',

src/core/services/tokenizer/subtitle-annotation-filter.ts

@@ -47,7 +47,6 @@ export const SUBTITLE_ANNOTATION_EXCLUDED_TERMS = new Set([
   'へえ',
   'ふう',
   'ほう',
-  'やはり',
   '何か',
   '何だ',
   '何も',
@@ -55,7 +54,6 @@ export const SUBTITLE_ANNOTATION_EXCLUDED_TERMS = new Set([
   '有る',
   '在る',
   '様',
-  '確かに',
   '誰も',
   '貴方',
   'もんか',