Require equityProfit; return null when balance invalid

computeDailyTarget now requires equityProfit (amount - accountSize) and
returns null when it's undefined/null/NaN. 0 is still a valid value.

- Removed totalProfit parameter (was only used as fallback)
- Callers handle null by skipping the account (eligibility) or throwing
  (execution paths)
- State API sets dailyTarget to null when no valid balance, avoids
  incorrect targetHit computation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/trading-logic.ts

@@ -80,16 +80,20 @@ export const POINT_VALUES: { [symbol: string]: number } = {
 export function computeDailyTarget(
     profitTarget: number,
     consistency: number,
-    totalProfit: number,
     dailyPnL: { date: string; pnl: number }[],
-    minDayPnL: number = 0,      // 0 = no minimum per day
-    minTradingDays: number = 0, // 0 = no minimum trading days
-    equityProfit?: number       // amount − accountSize; used for profitTarget comparison. Defaults to totalProfit.
-): { amount: number; path: 'first_day' | 'normal_day' | 'reduced_day' } {
+    minDayPnL: number,          // 0 = no minimum per day
+    minTradingDays: number,     // 0 = no minimum trading days
+    equityProfit: number | null | undefined // amount − accountSize. Null/undefined → skip (return null). 0 is valid.
+): { amount: number; path: 'first_day' | 'normal_day' | 'reduced_day' } | null {
+    // Don't run if we don't have a real account balance to compute against — 0 is valid.
+    if (typeof equityProfit !== 'number' || !Number.isFinite(equityProfit)) {
+        return null;
+    }
+
     const qualifyingDays = minDayPnL === 0 ? dailyPnL : dailyPnL.filter((d) => d.pnl >= minDayPnL);
     const daysTraded = qualifyingDays.length;
     const effectiveMinDay = Math.max(0, minDayPnL);
-    const currentProfit = equityProfit ?? totalProfit;
+    const currentProfit = equityProfit;
     const remaining = profitTarget - currentProfit;
 
     // 1. Profit target already met — coast on min-day if mandatory days remain, else nothing to do.