feat(app): the recovery phrase's words typed back are suggested from BIP-39's list (ADR 0017)

Each of the three fields suggests the words of BIP-39's whole English
list beginning with what is typed, never the phrase's own, and refuses a
word not on it as its field is left, so that a typo is caught before the
words are compared.

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

packages/halkyon_app/test/password/widget/phrase_check_fields_test.dart

@@ -0,0 +1,111 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_app/halkyon_app.dart';
+import 'package:halkyon_app/testing.dart';
+import 'package:material_ui/material_ui.dart';
+
+/// The recovery phrase's words typed back (ADR 0017): each field suggests
+/// words of BIP-39's whole English list as they are typed, never the
+/// phrase's own, and takes no word that isn't on it, so a typo is caught
+/// before the words are compared.
+void main() {
+  late List<TextEditingController> controllers;
+  late int done;
+
+  setUp(() {
+    controllers = [for (var i = 0; i < 3; i++) TextEditingController()];
+    done = 0;
+  });
+
+  tearDown(() {
+    for (final controller in controllers) {
+      controller.dispose();
+    }
+  });
+
+  Future<void> pump(WidgetTester tester) => tester.pumpWidget(
+    MaterialApp(
+      localizationsDelegates: testLocalizationsDelegates,
+      supportedLocales: HalkyonAppLocalizations.supportedLocales,
+      locale: const Locale('en'),
+      home: Scaffold(
+        body: SingleChildScrollView(
+          child: PhraseCheckFields(
+            positions: const [2, 7, 19],
+            controllers: controllers,
+            onDone: () => done++,
+          ),
+        ),
+      ),
+    ),
+  );
+
+  Finder field(int i) => find.byType(TextField).at(i);
+
+  testWidgets("the list's words are suggested as they are typed, and one "
+      'picked fills the field and moves on', (tester) async {
+    await pump(tester);
+    await tester.enterText(field(0), 'zo');
+    await tester.pump();
+
+    expect(find.text('zone'), findsOneWidget);
+    expect(find.text('zoo'), findsOneWidget);
+
+    await tester.tap(find.text('zoo'));
+    await tester.pump();
+    expect(controllers[0].text, 'zoo');
+    expect(
+      tester.widget<TextField>(field(1)).focusNode!.hasFocus,
+      isTrue,
+    );
+  });
+
+  testWidgets('a word typed whole suggests nothing more, unless a longer '
+      'one begins with it', (tester) async {
+    await pump(tester);
+    await tester.enterText(field(0), 'zoo');
+    await tester.pump();
+    // The field's own text alone, no option below it.
+    expect(find.text('zoo'), findsOneWidget);
+
+    await tester.enterText(field(0), 'act');
+    await tester.pump();
+    expect(find.text('action'), findsOneWidget);
+  });
+
+  testWidgets("a word that isn't on the list is refused as the field is "
+      'left, and the words are not handed on', (tester) async {
+    await pump(tester);
+    await tester.enterText(field(0), 'abandom');
+    await tester.testTextInput.receiveAction(TextInputAction.next);
+    await tester.pump();
+
+    expect(find.text('Not a word a recovery phrase is made of'), findsOne);
+    expect(
+      tester.widget<TextField>(field(0)).focusNode!.hasFocus,
+      isTrue,
+    );
+
+    await tester.enterText(field(0), 'abandon');
+    await tester.enterText(field(1), 'Zoo ');
+    await tester.enterText(field(2), 'qwerty');
+    await tester.testTextInput.receiveAction(TextInputAction.done);
+    await tester.pump();
+    expect(done, 0);
+    expect(find.text('Not a word a recovery phrase is made of'), findsOne);
+
+    await tester.enterText(field(2), 'ability');
+    await tester.pump();
+    await tester.testTextInput.receiveAction(TextInputAction.done);
+    await tester.pump();
+    expect(done, 1);
+    expect(find.text('Not a word a recovery phrase is made of'), findsNothing);
+  });
+
+  test("a phrase's word is one of BIP-39's English list, whatever its case "
+      'and the spaces around it', () {
+    expect(isPhraseWord(' Abandon '), isTrue);
+    expect(isPhraseWord('zoo'), isTrue);
+    expect(isPhraseWord('abandom'), isFalse);
+    expect(isPhraseWord(''), isFalse);
+  });
+}