Ledger Reconcile speed training

40/40 Ledger Reconcile simulations correct; first PB 9.499s→5.295s. Reuse: fixed A/B/C/D/E output slots; load openings, route each transaction by first letter and update that balance once, skip zero deltas, then emit fixed strings immediately—no sort/second pass. Net-delta bucketing was slower. Bottleneck: connector/network variance + 12-delta scan.