LC1 — the flag flip is ATOMIC (2.4). A permission row planted by direct SQL (invisible to
the delta, which reads metadata) makes the snapshot collide with
UQ_EntityFieldPermission_Field_Role midway. The save must report failure, the flag must
roll back to 0, and no snapshot rows may survive — only the planted poison row.
LC1 — the flag flip is ATOMIC (2.4). A permission row planted by direct SQL (invisible to the delta, which reads metadata) makes the snapshot collide with UQ_EntityFieldPermission_Field_Role midway. The save must report failure, the flag must roll back to 0, and no snapshot rows may survive — only the planted poison row.