fix(exec-dashboard): sort Top Threat Actors by uncovered techniques

Previously: alphabetical order (first 5 actors from list_actors query).
Now: ranked by uncovered technique count = technique_count × (1 - coverage_pct/100).
Tiebreak: higher technique_count first (broader attack surface).

Fetches 100 actors, sorts client-side, shows top 5 with:
- Rank badge (1-5) colored red/orange/yellow/gray
- 'N uncovered / M techniques' subtitle instead of target sectors
- Coverage bar + percentage

This ensures the actors with the largest coverage gap appear first.

frontend/src/pages/ExecutiveDashboardPage.tsx

@@ -155,9 +155,10 @@ export default function ExecutiveDashboardPage() {
     queryFn: getCoverageByTactic,
   });
 
+  // Fetch enough actors to rank properly — sort client-side by uncovered techniques
   const { data: threatActors } = useQuery({
     queryKey: ["threat-actors-top"],
-    queryFn: () => getThreatActors({ limit: 5 }),
+    queryFn: () => getThreatActors({ limit: 100 }),
   });
 
   const { data: allTechniques } = useQuery({
@@ -322,29 +323,50 @@ export default function ExecutiveDashboardPage() {
 
       {/* Section 3: Top Threat Actors */}
       <div className="rounded-xl border border-gray-800 bg-gray-900 p-4">
-        <h2 className="mb-3 text-sm font-semibold text-gray-300">
+        <h2 className="mb-1 text-sm font-semibold text-gray-300">
           Top Threat Actors
         </h2>
+        <p className="mb-3 text-[10px] text-gray-500">
+          Ranked by uncovered techniques (most exposure first)
+        </p>
         <div className="space-y-2">
-          {(threatActors?.items || []).map((actor) => (
+          {[...(threatActors?.items || [])]
+            // Sort by uncovered technique count DESC (= technique_count × gap%)
+            // Tiebreak: higher technique_count = broader attack surface
+            .sort((a, b) => {
+              const uncoveredA = a.technique_count * (1 - a.coverage_pct / 100);
+              const uncoveredB = b.technique_count * (1 - b.coverage_pct / 100);
+              if (uncoveredB !== uncoveredA) return uncoveredB - uncoveredA;
+              return b.technique_count - a.technique_count;
+            })
+            .slice(0, 5)
+            .map((actor, idx) => (
             <div
               key={actor.id}
               className="flex items-center gap-3 rounded-lg bg-gray-800/50 p-3 cursor-pointer hover:bg-gray-800"
               onClick={() => navigate(`/threat-actors/${actor.id}`)}
             >
-              <div className="flex h-8 w-8 items-center justify-center rounded-full bg-gray-700 text-xs font-bold text-gray-300">
+              {/* Rank badge */}
-                {actor.country?.slice(0, 2).toUpperCase() || "??"}
+              <div className={`flex h-6 w-6 shrink-0 items-center justify-center rounded-full text-[10px] font-bold ${
+                idx === 0 ? "bg-red-500/20 text-red-400"
+                : idx === 1 ? "bg-orange-500/20 text-orange-400"
+                : idx === 2 ? "bg-yellow-500/20 text-yellow-400"
+                : "bg-gray-700 text-gray-400"
+              }`}>
+                {idx + 1}
               </div>
               <div className="flex-1 min-w-0">
                 <p className="text-sm font-medium text-white truncate">
                   {actor.name}
                 </p>
                 <p className="text-[10px] text-gray-500 truncate">
-                  {actor.target_sectors?.slice(0, 3).join(", ")}
+                  {Math.round(actor.technique_count * (1 - actor.coverage_pct / 100))} uncovered
+                  {" / "}
+                  {actor.technique_count} techniques
                 </p>
               </div>
               <div className="flex items-center gap-2">
-                <div className="w-24 h-2 rounded-full bg-gray-700 overflow-hidden">
+                <div className="w-20 h-1.5 rounded-full bg-gray-700 overflow-hidden">
                   <div
                     className="h-full rounded-full transition-all"
                     style={{
@@ -358,8 +380,8 @@ export default function ExecutiveDashboardPage() {
                     }}
                   />
                 </div>
-                <span className="w-10 text-right text-xs font-medium text-gray-300">
+                <span className="w-10 text-right text-xs font-medium text-gray-300 tabular-nums">
-                  {actor.coverage_pct}%
+                  {actor.coverage_pct.toFixed(0)}%
                 </span>
               </div>
             </div>