Drop latest_timestamp fallback for release_date display

Showing the most recent eval timestamp as a "Released" date was misleading
when release_date is null. Render a dash instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/models/page.tsx

@@ -107,7 +107,7 @@ export default function ModelsPage() {
         case "name":
           return a.model_name.localeCompare(b.model_name)
         case "released":
-          return safeTimestamp(b.release_date ?? b.latest_timestamp) - safeTimestamp(a.release_date ?? a.latest_timestamp)
+          return safeTimestamp(b.release_date) - safeTimestamp(a.release_date)
         case "params":
           return (b.params_billions ?? 0) - (a.params_billions ?? 0)
         case "results":

components/model-table.tsx

@@ -127,7 +127,7 @@ export function ModelTable({
                   {row.developer}
                 </td>
                 <td className="font-mono text-[12px] text-[color:var(--fg-muted)] num">
-                  {formatDateShort(row.release_date ?? row.latest_timestamp)}
+                  {formatDateShort(row.release_date)}
                 </td>
                 <td className="font-mono text-[12px] text-[color:var(--fg-muted)]">
                   {formatParams(row)}