ci: run the backup suites

test_backup_manager.py existed but was never enrolled, so the tests that
should have guarded backup and restore have not run on a pull request.
That is part of why the restore bugs in the previous commit reached a
device: the suite was there, it just was not watching. Adds it alongside
the new registry-resolution tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Udr6MfaFLUPhX5Fgo67Jf5

.github/workflows/test.yml

@@ -82,4 +82,6 @@ jobs:
             test/test_install_preserves_existing.py \
             test/test_core_owned_config_keys.py \
             test/test_async_plugin_updates.py \
+            test/test_registry_id_resolution.py \
+            test/test_backup_manager.py \
             test/test_plugin_update_reservation.py