upstream matcher parity (filter.go: the plan prunes whole blocks, the exact seq window is applied client-side per row). found live by the new cutover smoke against production: the sweep delivered ~2 whole blocks of rows below the requested resume point. adds the cutover smoke example (archive sweep -> gapless cutover -> live tail, contiguity asserted through one handler) and a deliverBlock regression test. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>