feat(dictionary): characters of Chinese, Korean and Greek, written by hand; pinyin typed

Parity with Japanese's kanji and kana:

- The characters' tab is named by its language (Hanzi, Hangul & Hanja,
  Alphabet), its groups too: HSK levels and the characters in common use
  (Hong Kong's grades for traditional ones); Hangul and the Hanja taught
  in schools; Greek's letters. Radicals for Chinese and Korean in their
  own forms (讠 for 言 in simplified Chinese), none for Greek.
- A character's readings are named as its language names them: On and
  Kun, Pinyin, Eum and Hun (음, 훈); a letter means its sound and name.
- How characters are written comes by language: Chinese from Make Me a
  Hanzi (its medians in KanjiVG's square, Arphic Public License, a data
  file beside the app, never in cards), the Hangul letters drawn by the
  curator; a Korean word is written letter by letter (닭: ㄷ ㅏ ㄺ). Words
  of alphabets (German, Greek) aren't written by hand.
- A Chinese word's pinyin is typed in a session, tone numbers turning
  into marks (ni3 → nǐ); KRDict's levels (초급, 중급, 고급) tag Korean
  words; a Korean word's pronunciation shows in brackets ([가치]).
- Smaller: Look up in the composer keeps a noun's article; the Watch
  filter names its level list; hints and placeholders by language.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/test/feature/kanji/model/hangul_test.dart

@@ -0,0 +1,26 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_learn_flutter/src/feature/kanji/model/hangul.dart';
+
+void main() {
+  test('a Hangul syllable is written with its letters: the opening '
+      'consonant, the vowel and the closing one or cluster', () {
+    expect(hangulLetters('가'), ['ㄱ', 'ㅏ']);
+    expect(hangulLetters('닭'), ['ㄷ', 'ㅏ', 'ㄺ']);
+    expect(hangulLetters('쓰'), ['ㅆ', 'ㅡ']);
+    expect(hangulLetters('왜'), ['ㅇ', 'ㅙ']);
+    expect(hangulLetters('힣'), ['ㅎ', 'ㅣ', 'ㅎ']);
+    // What is no syllable stays as it is.
+    expect(hangulLetters('ㄱ'), ['ㄱ']);
+    expect(hangulLetters('食'), ['食']);
+  });
+
+  test('scripts whose strokes are drawn: Han characters, kana, Hangul; '
+      'not the alphabets', () {
+    expect(hasDrawnScript('食べる'), isTrue);
+    expect(hasDrawnScript('学习'), isTrue);
+    expect(hasDrawnScript('학교'), isTrue);
+    expect(hasDrawnScript('ㄱ'), isTrue);
+    expect(hasDrawnScript('das Haus'), isFalse);
+    expect(hasDrawnScript('Β β'), isFalse);
+  });
+}