feat: top-pick and open-trade status labels on the ticker page

Two read-only pills in the ticker header, beside the watchlist toggle:
- "Top Pick" when the ticker is the current #1 — the same ranking the dashboard
  highlights, via a shared topPickSymbol() helper so the two stay in sync.
- "Open Trade" when an open paper trade exists on the ticker.

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

frontend/src/lib/qualification.ts

@@ -49,6 +49,26 @@ export function qualifiesSetup(setup: TradeSetup, config: ActivationConfig): boo
   return true;
 }
 
+/**
+ * Symbol of the current single 'top pick' — the #1 row the dashboard highlights:
+ * the highest 12-1 momentum percentile among qualified setups (or among all
+ * setups when none qualify). Returns null when there are no setups. Keep in step
+ * with the Top Setups ranking in DashboardPage.
+ */
+export function topPickSymbol(
+  trades: TradeSetup[] | undefined,
+  activation: ActivationConfig | undefined,
+): string | null {
+  const all = trades ?? [];
+  if (all.length === 0) return null;
+  const qualified = activation ? all.filter((t) => qualifiesSetup(t, activation)) : [];
+  const pool = qualified.length > 0 ? qualified : all;
+  const top = [...pool].sort(
+    (a, b) => (b.momentum_percentile ?? -Infinity) - (a.momentum_percentile ?? -Infinity),
+  )[0];
+  return top?.symbol ?? null;
+}
+
 /** Short human summary of the active gate, e.g. for tooltips/labels. */
 export function activationSummary(config: ActivationConfig): string {
   const parts = [];