feat(studyset): a studyset's marker says what the instance sees of it (ADR 0019)

The developer's decision of 21 Oct, on the library's cards and the
studyset's Share in its action row alike:
- a lock: private, end-to-end encrypted;
- an open lock: readable by the instance, not published;
- a globe: published.

The lock and the open lock open one dialog saying what that means and
changing it (Make non-private; Make private, or Publish…, which opens the
Publish sheet, while it isn't private); a topic's dialog says its privacy
is its tree's. The globe opens the Publish sheet, whose status for a
studyset not published now says so ("Not published") with an open lock,
as "Private" means something else now. Texts in en and de.

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_localizations.dart

@@ -9468,7 +9468,7 @@ abstract class AppLocalizations {
   /// No description provided for @publishPrivate.
   ///
   /// In en, this message translates to:
-  /// **'Private · only you can see it'**
+  /// **'Not published · only you see it in Learn'**
   String get publishPrivate;
 
   /// No description provided for @publishPublished.
@@ -12266,6 +12266,54 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'The archive isn\'t encrypted: whoever has the file can read it.'**
   String get exportReadableNote;
+
+  /// No description provided for @studysetVisibilityReadable.
+  ///
+  /// In en, this message translates to:
+  /// **'Not private, not published'**
+  String get studysetVisibilityReadable;
+
+  /// No description provided for @studysetShareReadable.
+  ///
+  /// In en, this message translates to:
+  /// **'Share: not private'**
+  String get studysetShareReadable;
+
+  /// No description provided for @studysetPrivacyPrivateTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'“{title}” is private'**
+  String studysetPrivacyPrivateTitle(String title);
+
+  /// No description provided for @studysetPrivacyPrivateBody.
+  ///
+  /// In en, this message translates to:
+  /// **'Everything in it is end-to-end encrypted: only your devices can read it. The instance can\'t publish it, nor show it to Claude. Making it non-private decrypts it and syncs it again, so the instance can read it.'**
+  String get studysetPrivacyPrivateBody;
+
+  /// No description provided for @studysetPrivacyReadableTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'“{title}” isn\'t private'**
+  String studysetPrivacyReadableTitle(String title);
+
+  /// No description provided for @studysetPrivacyReadableBody.
+  ///
+  /// In en, this message translates to:
+  /// **'The instance can read it: you can publish it, and Claude can read it through the connector. Making it private encrypts it end to end on your devices; copies in the instance\'s backups stay readable until those expire.'**
+  String get studysetPrivacyReadableBody;
+
+  /// No description provided for @studysetPrivacyTopic.
+  ///
+  /// In en, this message translates to:
+  /// **'Its privacy is that of the studyset it\'s in.'**
+  String get studysetPrivacyTopic;
+
+  /// No description provided for @studysetPrivacyPublish.
+  ///
+  /// In en, this message translates to:
+  /// **'Publish…'**
+  String get studysetPrivacyPublish;
 }
 
 class _AppLocalizationsDelegate