feat: enrich correlation debug with fit_signal and orphan breakdown

_call_fits_incident now returns (bool, signal_str) so each correlation
decision records exactly what evidence fired: unit_overlap, vehicle_overlap,
location_proximity, time_fallback, tactical_default, or the corresponding
false-return variants (unit_loc_conflict, content_divergence, etc.).

- corr_fit_signal and corr_matched_units written to call docs for
  fast/single and fast/disambig paths
- Admin debug endpoint exposes the new fields in calls_detail
- Orphan section adds orphans_by_talkgroup summary (count, no-type count,
  sweep-exhausted count per TGID) and raises orphan limit 100 → 250
- Admin page shows corr_path and fit_signal distribution panels above raw
  JSON; time_fallback highlighted in yellow as a diagnostic marker

No correlation logic changed — diagnostic data only.

drb-frontend/app/admin/page.tsx

@@ -113,7 +113,28 @@ function CorrelationDebugTab() {
   }
 
   const json = data ? JSON.stringify(data, null, 2) : null;
-  const meta = data as { incident_count?: number; orphaned_call_count?: number; generated_at?: string } | null;
+  const meta = data as {
+    incident_count?: number;
+    orphaned_call_count?: number;
+    generated_at?: string;
+    incidents?: Array<{ calls_detail?: Array<{ corr_path?: string; corr_fit_signal?: string }> }>;
+    orphans_by_talkgroup?: Array<{ talkgroup_id?: number; talkgroup_name?: string; count: number; no_type_count: number; sweep_exhausted_count: number }>;
+  } | null;
+
+  // Aggregate corr_path and corr_fit_signal counts across all incident calls.
+  const pathCounts: Record<string, number> = {};
+  const signalCounts: Record<string, number> = {};
+  if (meta?.incidents) {
+    for (const inc of meta.incidents) {
+      for (const call of inc.calls_detail ?? []) {
+        const p = call.corr_path ?? "unknown";
+        pathCounts[p] = (pathCounts[p] ?? 0) + 1;
+        if (call.corr_fit_signal) {
+          signalCounts[call.corr_fit_signal] = (signalCounts[call.corr_fit_signal] ?? 0) + 1;
+        }
+      }
+    }
+  }
 
   return (
     <div className="space-y-4">
@@ -172,6 +193,46 @@ function CorrelationDebugTab() {
         </div>
       )}
 
+      {meta && Object.keys(pathCounts).length > 0 && (
+        <div className="grid grid-cols-2 gap-3">
+          <div className="bg-gray-900 border border-gray-800 rounded-xl p-4 space-y-1">
+            <p className="text-xs text-gray-400 font-mono font-semibold mb-2">corr_path distribution</p>
+            {Object.entries(pathCounts).sort((a, b) => b[1] - a[1]).map(([path, n]) => (
+              <div key={path} className="flex justify-between text-xs font-mono">
+                <span className="text-gray-300">{path}</span>
+                <span className="text-indigo-400">{n}</span>
+              </div>
+            ))}
+          </div>
+          <div className="bg-gray-900 border border-gray-800 rounded-xl p-4 space-y-1">
+            <p className="text-xs text-gray-400 font-mono font-semibold mb-2">fit_signal distribution</p>
+            {Object.keys(signalCounts).length === 0
+              ? <p className="text-xs text-gray-600 font-mono">No signal data yet — deploy correlator update first</p>
+              : Object.entries(signalCounts).sort((a, b) => b[1] - a[1]).map(([sig, n]) => (
+                  <div key={sig} className="flex justify-between text-xs font-mono">
+                    <span className={sig === "time_fallback" ? "text-yellow-400" : "text-gray-300"}>{sig}</span>
+                    <span className="text-indigo-400">{n}</span>
+                  </div>
+                ))
+            }
+          </div>
+        </div>
+      )}
+
+      {meta?.orphans_by_talkgroup && meta.orphans_by_talkgroup.length > 0 && (
+        <div className="bg-gray-900 border border-gray-800 rounded-xl p-4 space-y-1">
+          <p className="text-xs text-gray-400 font-mono font-semibold mb-2">orphans by talkgroup</p>
+          {meta.orphans_by_talkgroup.map((tg) => (
+            <div key={String(tg.talkgroup_id)} className="flex justify-between text-xs font-mono">
+              <span className="text-gray-300">{tg.talkgroup_name} <span className="text-gray-600">({tg.talkgroup_id})</span></span>
+              <span className="text-gray-400">
+                {tg.count} total · <span className="text-gray-500">{tg.no_type_count} no-type</span> · <span className="text-red-400">{tg.sweep_exhausted_count} exhausted</span>
+              </span>
+            </div>
+          ))}
+        </div>
+      )}
+
       {json && (
         <pre
           ref={preRef}