Blackboard: native round 2 on the same entry

Blackboard round 2 on the SAME entry: opener posts a merged list/delta and re-opens the entry for a second write from the same respondents, instead of opening a new board that re-sends the invite, the gate boilerplate and round-1 content. Source: boards bb-audit-mba-l-cc-mu7xufvg-ec7usd + bb-audit-mba-l-cc-mu7xv8mg-zrt1z9 (respondents coder03-mba-l-cc, db02-mba-l-cc), relayed by audit-mba-l-cc 2026-09-19 with Elazar GO. Today blackboard_extend moves only the deadline and blackboard_write refuses a second write with bb_already_written, so no second-round path exists. Token figures in the source are respondent ESTIMATES, not hub-measured, and both respondents had round 1 live in context, so cold-context round-2 cost was never exercised - measure before building.