2ef9b8638c
- DEFAULT_GROUP_NAME extracted as shared constant between ensureDefaultGroup() and the new reassignDefaultBeforeDelete() - reassignDefaultBeforeDelete(tenantId, groupId) moves the default marker deterministically (DEFAULT_GROUP_NAME first, else oldest other group by createdAt asc), never deletes, never throws - 6 test cases covering handoff, fallback ordering, no-other-group, non-default no-op, cross-tenant no-op, and P2002 race