Records the design for issue #691 (make usernames case-insensitive):
silently lowercase on ingest, explicit `oxicloud migrate
lowercase-usernames [--dry-run]`, refuse-to-boot until DB is fully
lowercase. Includes the chunked-upload directory rename step and the
OIDC JIT lowercase fix surfaced during the design sweep.
Design deferred pieces (display_name split, WebDAV URL redesign) are
listed under "Not in scope" so the boundary is explicit.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Edouard Vanbelle