Count CME holiday sessions as one combined trading day when the type opts in

Account types with the catalog's new combineCmeHolidays flag are read
through a combined-day view: holiday-session P&L entries fold into the
next full trading day (computed from the federal-holiday rules, so any
year works), the day count matches how the firm records it (Apex: Sun/
Mon/Tue around a Monday holiday is ONE day), and on the later sessions
of the stretch the earlier sessions' booked P&L carries into realized —
so day targets, already-traded gates, target-hit status and the panel's
day P&L all treat the stretch as a single day. Off by default; older
masters that don't send the flag behave exactly as before.

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

lib/firm-catalog.ts

@@ -155,8 +155,13 @@ function validatePayload(raw: unknown): FirmCatalogPayload {
             }
             if (!isStages(type.withdrawalStages)) throw new Error(`account type ${j} has bad withdrawalStages`);
             // Lenient like platform: a master from before the split toggle
-            // doesn't send the field, and those account types all split.
-            return { ...type, splitEnabled: type.splitEnabled !== false } as unknown as CatalogAccountType;
+            // doesn't send the field, and those account types all split. Same
+            // for CME holiday combining, where the old behavior was "off".
+            return {
+                ...type,
+                splitEnabled: type.splitEnabled !== false,
+                combineCmeHolidays: type.combineCmeHolidays === true,
+            } as unknown as CatalogAccountType;
         });
 
         return {