The ATTESTED VIEW combinator: this node is the derived cell whose rows are
over's rows joined against currently-applying attestation records under a
named requirement — both cells exist in the graph (the raw list AND the
signed list), and a consumer picks per edge. ref :x, gate: :req is sugar
that interposes an anonymous cell of exactly this shape.
mode: :annotate makes the view NON-BLOCKING: unsigned rows flow (best
effort) under the unsigned status instead of being withheld as pending.