Session rest: a rest across the 5 PM roll reports unsynced; health excuses a wake

A firm resting across the trade-date roll kept reporting its last snapshot,
so yesterday's realized P&L and DLL lockouts counted as accounts already
traded today (Nik's Topstep read 5/5 traded at 5:31 PM from 3:29 PM data).
Its report is now the unsynced one until it logs back in; a rest within one
trade date reports as before.

/api/health also counts a firm logging back in after a rest as nothing
wrong, within its 15-minute grace, rather than reading not ok for the
seconds before its first sync.

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

lib/trading-logic.ts

@@ -1889,6 +1889,17 @@ export function planRest(
     return { wakeAt, checkInAt: planCheckIn(now, wakeAt, rand), leadMs };
 }
 
+/**
+ * A resting session's snapshot, last synced at `lastSyncAt`, is from an
+ * earlier trade date than `now`: its realized P&L, DLL lockouts and legs are
+ * the old day's, and counted as today's they would read as accounts already
+ * traded. It reports as unsynced until the session logs back in.
+ */
+export function restSnapshotStale(lastSyncAt: number, now: number = Date.now()): boolean {
+    if (!(lastSyncAt > 0)) return true;
+    return currentTradeDateCT(new Date(lastSyncAt)) !== currentTradeDateCT(new Date(now));
+}
+
 /**
  * A firm's cap on how many of its accounts trade at once, on top of the
  * machine's own max concurrent accounts: keeps `items` in order, at most