fix(auth): a setup's password replaced ends the account's other sessions

The full reading's L4: password.set replacing the password of a setup never
finished (no authenticator confirmed yet) ended no session, against the
rule that every new password ends the account's other sessions. Now it
ends them all but the session asking, here and on every member (as a
change does; keepSession, which a member forwards).

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

@@ -251,6 +251,7 @@ final class _Register implements AccountRegister {
     String? code,
     bool freshGitHubSignIn = false,
     bool anonymousHere = false,
+    UuidValue? keepSession,
   }) => _answer('setPassword', () {
     add(person);
     passwords.add(person);