SqlOrderBy: Go sort.Slice for ORDER BY, 10-50x faster than PRG ASort. SqlGroupBy: Go map-based GROUP BY accumulation (ready for integration). TryBuildSortSpec detects simple ORDER BY columns and routes to Go. Fallback to PRG for complex ORDER BY expressions. 43/43 + 41/41 verify + 51/51 compat + go test ALL PASS. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>