Add per-account-type splitEnabled flag from the catalog

When the master marks an account type splitEnabled=false, big days trade
as one unsplit leg (the legacy one-and-done behavior); min-day bumps are
unaffected. Missing field — older master or pre-toggle cached catalog —
defaults to enabled.

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

lib/master-protocol.ts

@@ -70,6 +70,8 @@ export interface CatalogAccountType {
     maxLoss: number;
     maxPositionSize: number;
     targetSameEquity: boolean;
+    /** False = big days trade as one unsplit leg instead of random ≥$800 pieces. */
+    splitEnabled: boolean;
     withdrawalStages: { profit: number; consistency: number; minTradingDays: number }[];
     /** ISO. Ties between two matching account types are broken by this. */
     updatedAt: string;