Closes ART-OBSERVER-ADVANCE-AGGREGATE. Recomputes
artist_engagements.advancing_completed_count + advancing_total_count
on every section lifecycle event (created / updated-status-only /
deleted). Atomic via DB::transaction + lockForUpdate on both the
parent engagement and the sibling section rows; concurrent section-
status changes serialise correctly. Counter updates use
disableLogging() — counter sync is housekeeping, not audit. The
section's own updated event continues to log via LogsActivity on
AdvanceSection.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
