Eyes-on EXECUTE=true validation caught two bugs: (1) fractional qty -> all 6 orders cancelled (10243);
round to whole shares (skip if 0). (2) last_rebalance was set even when all orders were rejected,
which would block retry; now only marked when >=1 order is accepted.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>