Security review P2: a hard crash after the stage left the staged token
on disk. sweepCopySlots runs at start, before Credentials loads, and
removes each copy service slot whose binding holds no grant, plus any
staged temp file. It never touches a role's slots, a slot a loaded
reference names, or an organization whose document cannot be read. A
stage write that fails removes its temp file, and its slot when the
rename has already happened.
Build review P3s: push is held to the binding's approved level, not the
token's. Tests now cover the boot-copy pre-checks, the format check
running before the stage, and stageCopy's reference refusal.