Report each symbol's next-leg stats to the master; drop per-symbol commission

- lib/leg-estimate: an account's next leg sized on every surveyed
  candidate (planLegSize, ranked by rankForTarget) — notional, its
  multiple of the account and the broker's maximum, expected hold, cost
  and win chance. The dashboard's hold estimate and the reporter share it.
- The reporter sends it per DXtrade firm as symbolStats, for one live
  account from the largest prefix group with a leg left to trade.
- The symbol map's per-symbol commission is gone: the firm's applies.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/dxtrade-class.ts

@@ -1258,7 +1258,7 @@ export class DXTradeClient implements PlatformClient {
                     accountCurrency: ref.currency,
                 });
             if (rejection) { board.push({ symbol: cand.symbol, score: null, note: rejection }); continue; }
-            const pct = cand.commissionPct ?? firm?.commissionPct ?? 0;
+            const pct = firm?.commissionPct ?? 0;
             const score = scoreCandidate({
                 spreadFraction: spread,
                 commissionPct: pct,