Clear each customer's membership tag and each record tag wherever cached,
and always this namespace's collection tag. keys are exact deletes in this
instance's key space: the only bust a null client honours.
ProtectedsearchTags for a page: the scope its query searched (each customer's membership
tag, else the collection tag), so an empty page is bustable too, plus the
records it projects and the fields that chose or ordered its rows.
Root of the card hierarchy: the one
girasol-card-searchnamespace the customer and admin surfaces share, and the bust seam every writer inherits. Both surfaces project the same row, so one cached shape serves both.