fix(app): the short reading's nits on the device

- Deleting an identified account whose security can't be read (the
  instance out of reach) says so and deletes nothing; it went on to a
  deletion by the session alone, refused for an account with a password,
  and the person saw a spinner, then nothing. A refusal still leaves the
  session's own deletion.
- InstanceChoice's sharesStorage is required, so no app leaves it out and
  removes a folder another instance uses.
- A PasswordUnlock forgotten is spent: its secrets read again fail
  (StateError) rather than make a proof or a wrapping of zeros.

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/widget/account_tiles.dart

@@ -132,13 +132,23 @@ class const AccountTiles({
     try {
       security = identified ? await passwords.security() : null;
     } on Object catch (error) {
-      // Unreachable, or anything else (the reading of the fixes: a failure
-      // that isn't a refusal escaped, and the tap did nothing): deleting
-      // goes on, and fails as the session bloc says if it must.
+      if (error is PasswordFailed && error.problem != PasswordProblem.failed) {
+        // The instance refused to say (no passwords offered there): the
+        // session's own deletion, which the instance checks.
+        session.add(const SessionEventDeleteRequested());
+        return;
+      }
+      // Out of reach, or anything else: said so, nothing deleted (the short
+      // reading: a deletion by the session alone, refused for an account
+      // with a password, showed a spinner, then nothing).
       if (error is! PasswordFailed) {
         log('Reading the account failed: ${error.runtimeType}', name: 'Auth');
       }
-      session.add(const SessionEventDeleteRequested());
+      if (context.mounted) {
+        ScaffoldMessenger.maybeOf(
+          context,
+        )?.showSnackBar(SnackBar(content: Text(l10n.passwordFailed)));
+      }
       return;
     }
     if (security == null || !security.hasPassword) {