PlaceOffsiteRestore: live target via raw GetStackHDDPath not AppNamespaceRoot (F-3a-1a: no SSD
merge; undeployed refused), placement headroom gate (F-3a-1b), stat pre-pass over all placements
before any copy (F-3a-4: no partial writes), scratch removed on success/kept on failure (F-3a-2).
mapOffsiteRestorePaths refuses the namespace root itself (F-3a-3).
Delivery chain: DefaultEnabledEvents + GetNotificationPrefs append-if-absent migration + settings
checkbox + handler slice; paired with hub v0.55.0 allowlist (no customerMessages entry — raw
dynamic message survives). +8 tests; all 6 controller §10 red-proofs verified.
