Eviction now goes by the base's signal: `storeLost` and the `store-reset`
notice, with `bulwark-store-opened` as the marker and `prune-files` for files
with no key. The storage page and the lost count hang off that. What a user
picks is stored under `bulwark-offline-scope`, the key `offlineScopeFor`
reads, and `email-snapshot` follows the base's rule. `OfflineEnabled` is read
from the desktop bridge when it's there.