fix: coverage-aware event-study headline instead of misleading median delta

The "warned a median -18 days later" line was the median-over-1-event trap: the
coincident baseline's 60d median is a single lucky event, while breadth warned on
7. Replace it with the honest coverage framing (7/11 vs 1/11) and flag that the
median-lead comparison is unreliable when coverage differs this much.

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

frontend/src/pages/RegimePage.tsx

@@ -375,26 +375,25 @@ function EventStudyBody({ report }: { report: EventStudyReport }) {
   const recent = report.recent_breadth ?? [];
   const breadthVals = recent.map((r) => r.breadth);
   const divVals = recent.map((r) => r.divergence ?? 0);
-  const lead = report.lead_delta_days;
+  const moreCoverage = bd.events_with_signal > cd.events_with_signal;
   return (
     <div className="space-y-4">
       <p className="text-xs text-gray-500">
         {report.events?.length ?? 0} drawdown events (≥{report.params?.event_threshold_pct}%) on{' '}
-        {report.params?.benchmark} over ~5y. Higher median lead = earlier warning.
+        {report.params?.benchmark} over ~5y. With so few events, coverage (how many it warned before) matters
+        more than the median lead.
       </p>
       <div className="grid grid-cols-1 gap-2 sm:grid-cols-2">
-        <LeadStat label="Breadth divergence (leading candidate)" stats={bd} highlight={lead != null && lead > 0} />
+        <LeadStat label="Breadth divergence (leading candidate)" stats={bd} highlight={moreCoverage} />
         <LeadStat label="Coincident price composite (baseline)" stats={cd} />
       </div>
-      {lead != null && (
-        <p className="text-xs text-gray-400">
-          Breadth divergence warned a median{' '}
-          <span className={`font-medium ${lead > 0 ? 'text-emerald-400' : 'text-amber-400'}`}>
-            {lead > 0 ? '+' : ''}{lead} days
-          </span>{' '}
-          {lead >= 0 ? 'earlier' : 'later'} than the coincident baseline.
-        </p>
-      )}
+      <p className="text-xs text-gray-400">
+        Breadth divergence warned before{' '}
+        <span className="font-medium text-emerald-400">{bd.events_with_signal}/{bd.events_total}</span> drawdowns
+        {bd.median_lead_days != null ? ` (median ${bd.median_lead_days}d lead)` : ''}; the coincident baseline only{' '}
+        <span className="font-medium text-gray-300">{cd.events_with_signal}/{cd.events_total}</span>. The median-lead
+        comparison is unreliable when coverage differs this much — see per-drawdown below.
+      </p>
       {report.per_event && report.per_event.length > 0 && (
         <div className="space-y-1.5">
           <div className="text-[11px] uppercase tracking-wider text-gray-500">Per drawdown (same events, both indicators)</div>