Honor the catalog's min-legs setting and carve $500 pieces

Big days (> the $1,700 split threshold) must carve at least the account
type's minLegs from the catalog — pickLegAmount reserves the minimum
piece for each leg still owed, forcing a carve even once the residual
dips below the threshold, clamped to what the pieces allow. Days at or
below the threshold still trade as one leg. The smallest split piece
drops from $800 to $500. An older master without the field means no
minimum.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

types.ts

@@ -11,7 +11,8 @@ export interface AccountConfig {
     maxLoss: number;          // 0 = no limit; positive = account is "Dead" when loss exceeds this
     maxPositionSize: number;  // 0 = no limit; positive = max contracts per trade
     targetSameEquity: boolean;   // if true, reduce profitTarget by priorProfit after withdrawal
-    splitEnabled: boolean;    // false = big days trade as one unsplit leg instead of random ≥$800 pieces
+    splitEnabled: boolean;    // false = big days trade as one unsplit leg instead of random ≥$500 pieces
+    minLegs: number;          // big days (> $1,700) must carve at least this many legs (0 = however the carve falls)
     combineCmeHolidays: boolean;  // true = CME holiday sessions count with the next full trading day (Apex-style)
     withdrawalStages: { profit: number; consistency: number; minTradingDays: number }[];  // per-stage fresh profit + consistency (empty = use base values)
 }