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/core/chinese/pinyin_input_test.dart

@@ -0,0 +1,52 @@
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_learn_flutter/src/core/chinese/pinyin_input.dart';
+
+void main() {
+  test('tone numbers become tone marks: on a or e, on the o of ou, else on '
+      'the last vowel; ü typed as v or u:; the neutral tone unmarked', () {
+    expect(withToneMarks('ni3hao3'), 'nǐhǎo');
+    expect(withToneMarks('xue2xi2'), 'xuéxí');
+    expect(withToneMarks('dou1'), 'dōu');
+    expect(withToneMarks('gui4'), 'guì');
+    expect(withToneMarks('liu2'), 'liú');
+    expect(withToneMarks('lv4'), 'lǜ');
+    expect(withToneMarks('nu:3'), 'nǚ');
+    expect(withToneMarks('ma5'), 'ma');
+    expect(withToneMarks('Bei3jing1'), 'Běijīng');
+    expect(withToneMarks('xuéxí'), 'xuéxí');
+  });
+
+  test('pinyin compares with its tones, whatever its case, spaces and '
+      'numbers', () {
+    expect(pinyinKey('Xué xí'), 'xuéxí');
+    expect(pinyinKey('xue2 xi2'), 'xuéxí');
+    expect(pinyinKey("Xi1'an1"), 'xīān');
+    expect(givenPinyin('xíng, háng'), {'xíng', 'háng'});
+    expect(givenPinyin('xíng').contains(pinyinKey('xing2')), isTrue);
+    expect(givenPinyin('xíng').contains(pinyinKey('xing1')), isFalse);
+  });
+
+  test("pinyin is told from kana and from words' own letters", () {
+    expect(isPinyin('xué xí'), isTrue);
+    expect(isPinyin('shuō'), isTrue);
+    expect(isPinyin('たべる'), isFalse);
+    expect(isPinyin('가치'), isFalse);
+    expect(isPinyin(''), isFalse);
+  });
+
+  test('typing turns a syllable and its tone into the marked syllable, the '
+      'caret where it was typed', () {
+    const formatter = PinyinInputFormatter();
+    final value = formatter.formatEditUpdate(
+      const TextEditingValue(text: 'ni'),
+      const TextEditingValue(
+        text: 'ni3',
+        selection: TextSelection.collapsed(offset: 3),
+      ),
+    );
+
+    expect(value.text, 'nǐ');
+    expect(value.selection, const TextSelection.collapsed(offset: 2));
+  });
+}