The bank workspace whose dashboard domain is host, enabled or not, else
null: display data only, readable before any session and on a read-only
connection. Cached per host, a miss briefly; every bank write busts it.
Delete the cached entry for each host. The bank writer's seam: it passes every host the bank held before its write or holds now.
The read bank-dashboard makes before anyone has signed in: which bank workspace a host belongs to. Its cache shares the
bank-searchnamespace under its own key prefix; BankAdminService writes bust it through BankDashboardHostService.invalidate.