feat: sticky incident header with top-positioned action buttons (fix #5)

components/incidents/incident-detail.tsx

@@ -59,7 +59,7 @@ interface Props {
 function Field({ label, value }: { label: string; value: React.ReactNode }) {
   return (
     <div>
-      <dt className="text-xs text-gray-500 uppercase tracking-wide">{label}</dt>
+      <dt className="text-xs font-medium text-gray-700">{label}</dt>
       <dd className="text-sm text-gray-900 mt-0.5">{value ?? '—'}</dd>
     </div>
   )
@@ -107,12 +107,12 @@ export function IncidentDetail({ incident }: Props) {
       </div>
 
       <div className="bg-white rounded-xl shadow-sm p-5">
-        <h2 className="text-sm font-semibold text-gray-700 uppercase tracking-wide mb-2">Description</h2>
+        <h2 className="text-sm font-semibold text-gray-900 mb-2">Description</h2>
         <p className="text-sm text-gray-800 leading-relaxed whitespace-pre-wrap">{incident.description}</p>
       </div>
 
       <div className="bg-white rounded-xl shadow-sm p-5">
-        <h2 className="text-sm font-semibold text-gray-700 uppercase tracking-wide mb-3">
+        <h2 className="text-sm font-semibold text-gray-900 mb-3">
           Evidence — Report Stage
           <span className="ml-2 text-gray-400 font-normal normal-case">
             {reportStageFiles.length} file{reportStageFiles.length !== 1 ? 's' : ''}