feat: show current exposure instead of lifetime stats on the overview

The overview's Hit Rate and Expectancy were static lifetime aggregates — they
barely move day to day and aren't actionable at a glance. Replace them with the
current state from open paper trades:

- Open Risk: total $ at risk to stops across open positions.
- Unrealized: summed unrealized R (mark-to-market), with $ P&L and win/loss count.

Computed in the frontend from the already-loaded open trades (tradePnl) — no
backend change. The detailed lifetime stats remain on Signals → Track Record.

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

frontend/src/pages/DashboardPage.tsx

@@ -3,7 +3,7 @@ import { Link } from 'react-router-dom';
 import { useActivation } from '../hooks/useActivation';
 import { useTrades } from '../hooks/useTrades';
 import { useWatchlist } from '../hooks/useWatchlist';
-import { usePerformance } from '../hooks/usePerformance';
+import { usePaperTrades } from '../hooks/usePaperTrades';
 import { useMarketRegime } from '../hooks/useMarketRegime';
 import { regimeColor, regimeDot, regimeHeadline } from '../lib/regime';
 import { Callout } from '../components/ui/Callout';
@@ -11,6 +11,7 @@ import { Section } from '../components/ui/Section';
 import { OpenTradesPanel } from '../components/dashboard/OpenTradesPanel';
 import { SkeletonCard, SkeletonTable } from '../components/ui/Skeleton';
 import { formatPrice } from '../lib/format';
+import { tradePnl } from '../lib/paperTrade';
 import { recommendationActionLabel } from '../lib/recommendation';
 import { qualifiesSetup, activationSummary, primaryTargetProbability } from '../lib/qualification';
 import type { TradeSetup } from '../lib/types';
@@ -27,6 +28,11 @@ function rColor(value: number | null): string {
   return 'text-gray-300';
 }
 
+function money(value: number): string {
+  const sign = value >= 0 ? '+' : '−';
+  return `${sign}$${Math.abs(value).toFixed(2)}`;
+}
+
 function Metric({ label, value, sub, valueClass = 'text-gray-100' }: {
   label: string;
   value: string;
@@ -57,7 +63,7 @@ export default function DashboardPage() {
   const trades = useTrades();
   const watchlist = useWatchlist();
   const activation = useActivation();
-  const performance = usePerformance();
+  const openTrades = usePaperTrades('open');
   const regime = useMarketRegime();
 
   const qualifiedSetups = useMemo(
@@ -90,7 +96,21 @@ export default function DashboardPage() {
     weekday: 'long', month: 'long', day: 'numeric',
   });
 
-  const stats = performance.data?.overall;
+  // Current exposure from open paper trades: $ at risk to stops + mark-to-market.
+  const exposure = useMemo(() => {
+    const rows = openTrades.data ?? [];
+    let riskUsd = 0, unrealUsd = 0, unrealR = 0, rPriced = 0, winners = 0, losers = 0;
+    for (const t of rows) {
+      riskUsd += Math.abs(t.entry_price - t.stop_loss) * t.shares;
+      const p = tradePnl(t);
+      if (!p) continue;
+      unrealUsd += p.pnl;
+      if (p.r != null) { unrealR += p.r; rPriced += 1; }
+      if (p.pnl > 0) winners += 1;
+      else if (p.pnl < 0) losers += 1;
+    }
+    return { count: rows.length, riskUsd, unrealUsd, unrealR, rPriced, winners, losers };
+  }, [openTrades.data]);
 
   return (
     <div className="space-y-8 animate-slide-up">
@@ -120,7 +140,7 @@ export default function DashboardPage() {
       )}
 
       {/* Metric strip */}
-      {(trades.isLoading || performance.isLoading) ? (
+      {(trades.isLoading || openTrades.isLoading) ? (
         <div className="grid gap-4 sm:grid-cols-2 lg:grid-cols-4">
           <SkeletonCard /><SkeletonCard /><SkeletonCard /><SkeletonCard />
         </div>
@@ -138,15 +158,19 @@ export default function DashboardPage() {
             valueClass={qualifiedSetups.length > 0 ? 'text-blue-300' : 'text-gray-100'}
           />
           <Metric
-            label="Hit Rate"
-            value={stats?.hit_rate != null ? `${stats.hit_rate.toFixed(1)}%` : '—'}
-            sub={stats ? `${stats.wins}W / ${stats.losses}L evaluated` : 'no outcomes yet'}
+            label="Open Risk"
+            value={exposure.count > 0 ? `$${exposure.riskUsd.toFixed(0)}` : '—'}
+            sub={exposure.count > 0 ? `${exposure.count} open · risk to stops` : 'no open trades'}
           />
           <Metric
-            label="Expectancy"
-            value={fmtR(stats?.avg_r ?? null)}
-            valueClass={rColor(stats?.avg_r ?? null)}
-            sub="average R per trade"
+            label="Unrealized"
+            value={exposure.rPriced > 0 ? fmtR(exposure.unrealR) : '—'}
+            valueClass={rColor(exposure.rPriced > 0 ? exposure.unrealR : null)}
+            sub={
+              exposure.count > 0
+                ? `${money(exposure.unrealUsd)} · ${exposure.winners}▲ ${exposure.losers}▼`
+                : 'mark-to-market'
+            }
           />
         </div>
       )}