feat(app): type a word's reading while studying

A new study option, Type the reading (settings schema 6, beside the
vocabulary quiz; turning one on turns the other off): a word with kanji
shows alone, and its reading is typed, in kana; romaji turn into kana as
they are typed (doubled consonants, n before a consonant, nn and n'), and
the device's own Japanese input works as it does. Check, or Enter, says
whether it was right (katakana counts as hiragana) and what was typed
beside the reading, then shows the meanings and the ratings; the person
still rates, as Anki's typed answers have it. A word written in kana, one
usually written so, and a card asked back first flip as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/test/feature/settings/model/person_settings_test.dart

@@ -83,7 +83,7 @@ void main() {
       ),
     );
 
-    expect(settingsSchemaVersion, 5);
+    expect(settingsSchemaVersion, greaterThanOrEqualTo(5));
     expect(decodeSettingsPayload(encodeSettingsPayload(settings)), settings);
     expect(
       decodeSettingsPayload(
@@ -96,6 +96,20 @@ void main() {
     );
   });
 
+  test('typing readings survives a round trip, in the sixth schema; a '
+      'payload from before has it off', () {
+    const settings = PersonSettings(study: StudyOptions(typeReadings: true));
+
+    expect(settingsSchemaVersion, 6);
+    expect(decodeSettingsPayload(encodeSettingsPayload(settings)), settings);
+    expect(
+      decodeSettingsPayload(
+        encodePayload(5, {'studyTags': {}, 'study': {}}),
+      ).study.typeReadings,
+      isFalse,
+    );
+  });
+
   test('study options keep their numbers in range', () {
     final options = const StudyOptions().copyWith(
       cardsPerRound: 50,