fix: use String() instead of .toISOString() for errand timestamps

tRPC without superjson serializes Date objects as plain strings/numbers
over the wire. The .toISOString() calls crashed because the values
aren't Date instances on the client. Matches the existing pattern used
elsewhere (e.g. agents page).

apps/web/src/components/ErrandDetailPanel.tsx

@@ -331,8 +331,8 @@ export function ErrandDetailPanel({ errandId, onClose }: ErrandDetailPanelProps)
                     {/* Info line */}
                     <div className="px-5 pt-4 text-sm text-muted-foreground">
                       {errand.status === 'merged'
-                        ? `Merged into ${errand.baseBranch} · ${formatRelativeTime(errand.updatedAt.toISOString())}`
-                        : `Abandoned · ${formatRelativeTime(errand.updatedAt.toISOString())}`}
+                        ? `Merged into ${errand.baseBranch} · ${formatRelativeTime(String(errand.updatedAt))}`
+                        : `Abandoned · ${formatRelativeTime(String(errand.updatedAt))}`}
                     </div>
 
                     {/* Read-only diff */}

apps/web/src/routes/errands/index.tsx

@@ -103,7 +103,7 @@ function ErrandsPage() {
                     {e.agentAlias ?? '—'}
                   </td>
                   <td className="px-4 py-3 text-muted-foreground whitespace-nowrap">
-                    {formatRelativeTime(e.createdAt.toISOString())}
+                    {formatRelativeTime(String(e.createdAt))}
                   </td>
                 </tr>
               ))}