Add day-plan double-count diagnostics

The daily target sometimes inflates to base + consistency×todayPnL (e.g.
1200 + 0.4×1218.48 = 1687.39), which happens when a session's cached
daily-P&L row is dated something other than the current tradeDate: it
then lands in BOTH the prior-day list and realizedPnL, so day-start
equity reads too low while the prior-day sum stays high.

Detect it with a book-balance invariant that is coincidence-proof (it
does not care whether prior and today P&L happen to be equal): the
reconstructed day-start equity (equityProfit − realizedPnL) must equal
priorProfit + sum(prior days). The state route now logs the full account
state whenever those disagree by more than $50, and GET /api/debug
reports the same per-account breakdown on demand (?account=<substring>)
so the exact inputs can be captured the moment a number looks wrong.

Read-only; no behavior change. Remove once the trigger is fixed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/api/state/route.ts

@@ -93,6 +93,49 @@ export async function GET() {
                     const consistencyReal = (effective.consistency > 0 && effective.consistency < 1 && maxDay > 0)
                         ? maxDay / effective.consistency : 0;
                     effectiveProfitTarget = Math.max(effective.profitTarget, consistencyReal);
+
+                    // ── Double-count diagnostic ───────────────────────────────
+                    // computeDayPlan reconstructs day-start equity as
+                    // equityProfit − realizedPnL, then treats every dailyPnL row
+                    // NOT dated today as a prior day. Those two views must agree:
+                    // day-start equity should equal priorProfit + sum(prior days).
+                    // When a session's cached row is dated something other than
+                    // today's tradeDate, that session lands in BOTH the prior-day
+                    // list and realizedPnL — day-start equity reads too low while
+                    // the prior sum stays high, and the daily target inflates to
+                    // base + consistency×todayPnL (the $1,687.39 symptom). Fires
+                    // only when the books disagree by > $50, logging the exact
+                    // state needed to diagnose the trigger. Remove once resolved.
+                    const priorDaysSum = dailyPnL
+                        .filter((d) => d.date !== combined.tradeDate)
+                        .reduce((s, d) => s + d.pnl, 0);
+                    const dayStartEquity = equityProfit - combined.realizedPnL;
+                    const expectedDayStart = priorProfit + priorDaysSum;
+                    const drift = Math.round((dayStartEquity - expectedDayStart) * 100) / 100;
+                    if (Math.abs(drift) > 50) {
+                        console.warn('[day-plan][equity-drift] ' + JSON.stringify({
+                            account: acc.name,
+                            id: acc.id,
+                            serverNow: new Date().toISOString(),
+                            tradeDate: combined.tradeDate,
+                            drift,
+                            dayStartEquity,
+                            expectedDayStart,
+                            equityProfit,
+                            realizedPnL: combined.realizedPnL,
+                            priorProfit,
+                            priorDaysSum,
+                            dayTarget: plan?.dayTarget ?? null,
+                            remainingToday: plan?.remainingToday ?? null,
+                            consistency: effective.consistency,
+                            effectiveProfitTarget,
+                            hasTodayRow: dailyPnL.some((d) => d.date === combined.tradeDate),
+                            combineCmeHolidays: cfg.combineCmeHolidays === true,
+                            combinedDailyPnL: dailyPnL,
+                            rawDailyPnL: client.dailyPnL[acc.id] ?? [],
+                        }));
+                    }
+
                     // Condition 1: profit target already exceeded (target=0), still need days → any activity counts
                     // Condition 2: target > 0 → all legs done (day's remaining target used up)
                     if (plan) {