NO content authored here — this commits the long-uncommitted LIVE hotfix from
incident 2026-06-12 (bars_held UInt16 poison jammed 18M rows 1.5d): poison rows
retried individually after CH_POISON_ATTEMPTS, then quarantined to dead_letter;
includes the ids loop-variable bugfix. Uncommitted live code was one checkout
away from loss.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>