fix(achievements): Graduate achievements only unlock when all kanji for the specific JLPT level are mastered

[Copilot]

checkContentMastery for contentType === 'kanji' ignored jlptLevel entirely — it checked whatever kanji happened to be in characterMastery, so practicing a handful of N5 kanji with ≥80% accuracy trivially satisfied N4–N1 Graduate checks as well.

Root cause

// Before — jlptLevel from achievement.requirements.additional is never used
} else if (contentType === 'kanji') {
  relevantEntries = entries.filter(([key]) => isSingleKanji(key)); // all kanji, any level
}

Changes

• store/kanjiSets.ts (new) — Static Set<string> per JLPT level extracted from public/data-kanji/*.json (N5: 80, N4: 167, N3: 370, N2: 374, N1: 1504 chars), plus a KANJI_BY_JLPT_LEVEL lookup map. Same pattern as the existing BASIC_HIRAGANA/BASIC_KATAKANA sets.

• checkContentMastery — Kanji branch now requires jlptLevel, scopes relevantEntries to only that level's set, and guards relevantEntries.length < kanjiSet.size so all kanji in the level must have been practiced before the achievement can unlock:

  } else if (contentType === 'kanji') {
    const jlptLevel = additional?.jlptLevel;
    if (!jlptLevel) return false;
    const kanjiSet = KANJI_BY_JLPT_LEVEL[jlptLevel];
    relevantEntries = entries.filter(([key]) => kanjiSet.has(key));
    if (relevantEntries.length < kanjiSet.size) return false;
  }

• useAchievementProgress.ts — Progress for kanji Graduate achievements now displays masteredCount / kanjiSet.size (count of level-specific kanji at ≥80% accuracy) instead of a static 0%.

• __tests__/kanjiGraduate.test.ts (new) — Regression tests covering: correct set sizes, practicing only N5 does not unlock N4–N1, partial N5 practice does not unlock N5, below-threshold accuracy does not unlock, and each level checks its own set.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[BUG] N4 to N1 Graduate achievements achieved before completed</issue_title>
<issue_description>## 🐛 Bug Description

I was just finished my first session in Kanji dojo practicing the level 1 in N5. After I completed the session, I've got a few achievements, some of them are the N5 to N1 Graduate which requires 80% of accuracy on the practices of each level. Since I only practiced N5 Kanji Training once, and haven't tried any other units yet, I don't think I'm supposed to get the Graduate achievements for N4 to N1.

📋 Steps to Reproduce

1. Start a Kanji Training for the first time and finish it.
2. You'll get the achievements mentioned before.

🎯 Expected Behavior

User should get the Graduate achievements according to what units they practiced.

📸 Screenshots

📱 Environment Information

• Browser: Cromite 145.0.7632.120
• Operating System: Android 14
• Device: Mobile

🔍 Additional Context

None

Thank you for helping improve KanaDojo! 🙏
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [BUG] N4 to N1 Graduate achievements achieved before completed #6961

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