moveColorsToStart now reports whether the left edge was confirmed by stable signatures and retries anchor failures with another color node (within the horizontal swipe budget). The reverse-sweep skip is allowed only for row 0 of the first vertical pass when the sweep began at a confirmed left edge; otherwise the full snake sweep is kept. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01NTDbDcwbDw1TSAcE6wfh2F