Live apply now accepts only :5433/agent_system_dev plus a data/dev
host root, maps stored work dirs fail-closed, and reports unique
O_EXCL backups after a parent-directory fsync.
Co-authored-by: Cursor <cursoragent@cursor.com>
Default still refuses shared DSN/paths. Apply to dev requires --live,
--environment dev, a single --doc-id, and confirm REPAIR_SINGLE_DEV_DOC.
Co-authored-by: Cursor <cursoragent@cursor.com>