fix(profile): the handle's hint says it is private until the profile is public (ADR 0020, D5)

A handle alone is private: its page and `profiles.byHandle` answer as
for a handle nobody has until its person fills in their profile or
publishes something. The hint under it said "Others find you as @…"
all the same, also after removing a profile (D27). It now says it is
private until then, by the rule the instance's `isPublic` applies.

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

apps/learn/halkyon_learn_flutter/lib/l10n/app_de.arb

@@ -485,6 +485,8 @@
   "publicProfileHandleHint": "Buchstaben, Ziffern und Unterstriche, bis zu 30",
   "publicProfileAddress": "Andere finden dich als @{address}",
   "@publicProfileAddress": {"placeholders": {"address": {"type": "String"}}},
+  "publicProfileAddressPrivate": "Privat, bis du dein Profil ausfüllst oder etwas veröffentlichst; dann finden dich andere als @{address}.",
+  "@publicProfileAddressPrivate": {"placeholders": {"address": {"type": "String"}}},
   "publicProfileHandleFixed": "Fest, seit du veröffentlicht hast: Andere verweisen darauf.",
   "publicProfileBio": "Über dich",
   "publicProfileLinks": "Links",

apps/learn/halkyon_learn_flutter/lib/l10n/app_en.arb

@@ -550,6 +550,8 @@
   "publicProfileHandleHint": "Letters, digits and underscores, up to 30",
   "publicProfileAddress": "Others find you as @{address}",
   "@publicProfileAddress": {"placeholders": {"address": {"type": "String"}}},
+  "publicProfileAddressPrivate": "Private until you fill in your profile or publish something; then others find you as @{address}.",
+  "@publicProfileAddressPrivate": {"placeholders": {"address": {"type": "String"}}},
   "publicProfileHandleFixed": "Fixed since you published: others refer to it.",
   "publicProfileBio": "Bio",
   "publicProfileLinks": "Links",

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations.dart

@@ -2914,6 +2914,12 @@ abstract class AppLocalizations {
   /// **'Others find you as @{address}'**
   String publicProfileAddress(String address);
 
+  /// No description provided for @publicProfileAddressPrivate.
+  ///
+  /// In en, this message translates to:
+  /// **'Private until you fill in your profile or publish something; then others find you as @{address}.'**
+  String publicProfileAddressPrivate(String address);
+
   /// No description provided for @publicProfileHandleFixed.
   ///
   /// In en, this message translates to:

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations_de.dart

@@ -1766,6 +1766,11 @@ class AppLocalizationsDe extends AppLocalizations {
     return 'Andere finden dich als @$address';
   }
 
+  @override
+  String publicProfileAddressPrivate(String address) {
+    return 'Privat, bis du dein Profil ausfüllst oder etwas veröffentlichst; dann finden dich andere als @$address.';
+  }
+
   @override
   String get publicProfileHandleFixed =>
       'Fest, seit du veröffentlicht hast: Andere verweisen darauf.';

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -1750,6 +1750,11 @@ class AppLocalizationsEn extends AppLocalizations {
     return 'Others find you as @$address';
   }
 
+  @override
+  String publicProfileAddressPrivate(String address) {
+    return 'Private until you fill in your profile or publish something; then others find you as @$address.';
+  }
+
   @override
   String get publicProfileHandleFixed =>
       'Fixed since you published: others refer to it.';

apps/learn/halkyon_learn_flutter/lib/src/feature/profile/widget/public_profile_section.dart

@@ -342,6 +342,10 @@ class _ProfileFormState() extends State<_ProfileForm> {
           onTap: fixed ? null : _chooseHandle,
           helperText: switch (profile) {
             PublicProfile(handleFixed: true) => l10n.publicProfileHandleFixed,
+            // Its handle alone is private (ADR 0020, D5), as the instance's
+            // `isPublic` has it: nothing published, nothing filled in.
+            final profile? when !_showsSomething(profile) =>
+              l10n.publicProfileAddressPrivate(profile.address),
             final profile? => l10n.publicProfileAddress(profile.address),
             null => l10n.publicProfileHandleFirst,
           },

apps/learn/halkyon_learn_flutter/test/feature/profile/public_profile_test.dart

@@ -16,6 +16,12 @@ import '../../support/fake_profile_gateway.dart';
 import '../../support/pump_app.dart';
 import '../../support/test_dependencies.dart';
 
+/// The handle's hint while the profile is public, and while it is not.
+const publicHint = 'Others find you as @raisondetredev@halkyon.eu';
+const privateHint =
+    'Private until you fill in your profile or publish something; then '
+    'others find you as @raisondetredev@halkyon.eu.';
+
 void main() {
   /// Opens the Profile tab of a person whose profile the instance answers
   /// through [profiles].
@@ -92,10 +98,7 @@ void main() {
     await tester.tap(find.widgetWithText(FilledButton, 'Choose'));
     await tester.pumpAndSettle();
 
-    expect(
-      find.text('Others find you as @raisondetredev@halkyon.eu'),
-      findsOneWidget,
-    );
+    expect(find.text(publicHint), findsOneWidget);
     expect(find.text('@raisondetredev'), findsOneWidget);
     expect(profiles.profile!.displayName, 'Tizian');
     expect(profiles.profile!.bio, 'Learning Japanese.');
@@ -244,12 +247,14 @@ void main() {
       find.widgetWithText(TextField, 'https://halkyon.app'),
       findsNothing,
     );
-    // Nothing is left to remove.
+    // Nothing is left to remove, and the handle is private again.
     expect(find.text('Remove profile'), findsNothing);
+    expect(find.text(privateHint), findsOneWidget);
   });
 
   testWidgets('offers no removing while nothing is filled in: the handle '
-      'alone is private already', (tester) async {
+      'alone is private already, as its hint says (ADR 0020, D5), until '
+      'something is filled in', (tester) async {
     await showProfile(
       tester,
       FakeProfileGateway(
@@ -262,6 +267,15 @@ void main() {
 
     expect(find.text('@raisondetredev'), findsOneWidget);
     expect(find.text('Remove profile'), findsNothing);
+    expect(find.text(privateHint), findsOneWidget);
+    expect(find.text(publicHint), findsNothing);
+
+    await tester.enterText(field('Display name'), 'Tizian');
+    await tester.testTextInput.receiveAction(TextInputAction.done);
+    await tester.pumpAndSettle();
+
+    expect(find.text(publicHint), findsOneWidget);
+    expect(find.text(privateHint), findsNothing);
   });
 
   testWidgets('a saved profile takes a picture as its avatar, and gives it '