Rules with Expiration{Date: <past>} route through ScanAtDate in the
engine (decideMode's ActionKindExpirationDate case) — a separate
compile + dispatch branch from the EventDriven delay-group path the
Days-based tests exercise.
Past date + in-prefix object → must expire. Out-of-prefix object →
must remain. Object also backdated as defense-in-depth so the
assertion doesn't depend on whether the dispatcher consults
MinTriggerAge for date kinds.
Chris Lu
957ac1335c