fix(app): signing out or deleting the account keeps the person's app until it is done

Both went through the launch screen (SessionStateLoading), which closed the
person's app before asking the instance; a failure then opened it again
with no word of why. The person's state stays now, saying what is under
way (`busy`), and a failure keeps them signed in with why (`problem`). An
instance out of reach still signs out on the device (Serverpod's
signOutDevice), as signing out of a borrowed device must work offline, so
only the device's own storage fails a sign-out; a deletion fails whenever
the instance isn't reached or refuses.

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/lib/src/auth/bloc/session_bloc.dart

@@ -126,28 +126,49 @@ class SessionBloc(final AuthRepository _auth, final SignedOutMark _mark)
   Future<void> _onSignOutRequested(
     SessionEventSignOutRequested event,
     Emitter<SessionState> emit,
-  ) async {
-    emit(const SessionStateLoading());
-    try {
-      // The status change to signed out then asks how to start.
-      await _auth.signOut();
-    } on Object catch (error, st) {
-      addError(error, st);
-      emit(_stateOf(_auth.status));
-    }
-  }
+  ) => _onAccountAction(
+    SessionAction.signOut,
+    // The instance out of reach signs out on this device all the same
+    // (Serverpod's `signOutDevice`), as signing out of a borrowed device
+    // must work offline; only the device's own storage fails it.
+    _auth.signOut,
+    SessionProblem.signOutFailed,
+    emit,
+  );
 
   Future<void> _onDeleteRequested(
     SessionEventDeleteRequested event,
     Emitter<SessionState> emit,
+  ) => _onAccountAction(
+    SessionAction.delete,
+    _auth.deleteAccount,
+    SessionProblem.deleteFailed,
+    emit,
+  );
+
+  /// Runs [action] for the signed-in person's account, their app in place
+  /// meanwhile, [busy] saying what is under way: never through the launch
+  /// screen ([SessionStateLoading]), which would close the app and, should
+  /// [action] fail, open it again with no word of why. Done, the status
+  /// change to signed out asks how to start; failed, the person stays,
+  /// told so by [problem].
+  Future<void> _onAccountAction(
+    SessionAction busy,
+    Future<void> Function() action,
+    SessionProblem problem,
+    Emitter<SessionState> emit,
   ) async {
-    emit(const SessionStateLoading());
+    if (_auth.status case final SignedIn person) {
+      emit(SessionStateActive(person, busy: busy));
+    }
     try {
-      // The status change to signed out then asks how to start.
-      await _auth.deleteAccount();
+      await action();
     } on Object catch (error, st) {
       addError(error, st);
-      emit(_stateOf(_auth.status));
+      emit(switch (_auth.status) {
+        final SignedIn person => SessionStateActive(person, problem: problem),
+        SignedOut() => const SessionStateSignedOut(),
+      });
     }
   }
 
@@ -219,10 +240,40 @@ final class const SessionStateFailed() extends SessionState {
 /// A person is signed in.
 final class const SessionStateActive(
   /// Who is signed in.
-  final SignedIn person,
-) extends SessionState {
+  final SignedIn person, {
+
+  /// What is under way for the account (signing out, deleting it), while
+  /// the person's app stays; null for nothing.
+  final SessionAction? busy,
+
+  /// Why the last of those failed, the person still signed in; null for
+  /// none.
+  final SessionProblem? problem,
+}) extends SessionState {
   @override
-  List<Object?> get props => [person];
+  List<Object?> get props => [person, busy, problem];
+}
+
+/// What the person asked for their account, under way while their app
+/// stays.
+enum SessionAction() {
+  /// Signing out.
+  signOut,
+
+  /// Deleting the account.
+  delete,
+}
+
+/// Why signing out or deleting the account failed, the person still signed
+/// in.
+enum SessionProblem() {
+  /// Signing out failed on this device: the instance not reached signs out
+  /// here all the same, so only the device's own storage fails it.
+  signOutFailed,
+
+  /// Deleting the account failed, the instance not reached or refusing:
+  /// nothing deleted.
+  deleteFailed,
 }
 
 /// [person] signed in with GitHub just now: before their app, a password