feat(tag-vocab): NoteRepository — getTopUsedTags + getTagIdByName (#3 v0.2.3)

- getTopUsedTags(limit=20): top-N (count desc, id asc) + kebab-case 필터 + deleted_at 제외
- getTagIdByName(name): COLLATE NOCASE lookup
- AI+user source 통합 카운트 (Q1=C 결정)
- 단위 +7 cases (정렬, 필터, source 통합, deleted 제외, limit, getTagIdByName)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main/repository/NoteRepository.ts

@@ -215,6 +215,40 @@ export class NoteRepository {
       .run(nextRunAt, lastError.slice(0, 500), noteId);
   }
 
+  /**
+   * v0.2.3 #3 — AI prompt 의 vocabulary 후보. 사용 빈도 높은 태그 top-N.
+   * source 무시 (AI+user 통합), kebab-case 통과한 것만 (한글/공백/대문자 제외).
+   * deleted_at IS NULL 만 (휴지통 노트 태그 제외).
+   */
+  getTopUsedTags(limit = 20): string[] {
+    const rows = this.db
+      .prepare(
+        `SELECT t.name, COUNT(*) c
+           FROM tags t
+           JOIN note_tags nt ON nt.tag_id = t.id
+           JOIN notes n ON n.id = nt.note_id
+          WHERE n.deleted_at IS NULL
+          GROUP BY t.id
+          ORDER BY c DESC, t.id ASC
+          LIMIT ?`
+      )
+      .all(limit) as Array<{ name: string; c: number }>;
+    return rows
+      .map((r) => r.name)
+      .filter((n) => /^[a-z0-9-]+$/.test(n));
+  }
+
+  /**
+   * v0.2.3 #3 — vocab hit telemetry 의 tagId 확보용. updateAiResult 후 호출 보장.
+   * tags.name COLLATE NOCASE 라 case-insensitive lookup.
+   */
+  getTagIdByName(name: string): number | null {
+    const row = this.db
+      .prepare(`SELECT id FROM tags WHERE name = ? COLLATE NOCASE LIMIT 1`)
+      .get(name) as { id: number } | undefined;
+    return row ? row.id : null;
+  }
+
   updateUserAiFields(
     id: string,
     fields: { title?: string; summary?: string; tags?: string[] }