fix(auth): a member asks the register whose account it is before a deletion's proof counts

The reading of the full reading's fixes found (B1) that a member asked
the register knownAccounts inside the owner-proof try, so ten tries to
delete while the register was out of reach ended the owner's session,
though no proof ever left the member; and that a person anonymous on a
member could no longer delete their account while the register was down.

The member now asks first, outside the try, which wraps only what checks
the proof. While the register is out of reach, a person still anonymous
here (becoming identified ends that) is none of its and is deleted here;
anyone else waits for the register.

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_base_server/test/integration/register/member_test.dart

@@ -1060,6 +1060,41 @@ void main() {
           );
           expect(hostDeleted, isEmpty);
         });
+
+        test('asks the register first: tries while it is out of reach count '
+            "for nothing, as no proof left here (the reading of the fixes' "
+            'B1)', () async {
+          register.failing = RegisterUnavailableException('test');
+          DeletionProof proof() => DeletionProof(
+            challenge: const Uuid().v7obj(),
+            clientValue: ByteData(384),
+            clientProof: ByteData(32),
+            totpCode: '123456',
+            instanceUrl: testInstanceUrl,
+          );
+          for (var i = 0; i < 11; i++) {
+            await expectLater(
+              endpoints.account.delete(asBen(), proof: proof()),
+              throwsA(isA<RegisterUnavailableException>()),
+            );
+          }
+          expect(register.asked.toSet(), {'knownAccounts'});
+          expect(
+            await ServerSideSession.db.findById(session, bensLaptop),
+            isNotNull,
+          );
+        });
+
+        test('of a person anonymous here deletes it here while the register '
+            'is out of reach: becoming identified ends being anonymous, so '
+            "none is the register's", () async {
+          register.failing = RegisterUnavailableException('test');
+
+          await endpoints.account.delete(asAnna());
+
+          expect(await AuthUser.db.findById(session, anna), isNull);
+          expect(hostDeleted, [anna]);
+        });
       });
 
       group('told by the register that an account is gone', () {