fix: use self-portaling DetailPanel from design system v0.1.5

DetailPanel now portals itself to #cameleer-detail-panel-root (a div
AppShell places as a sibling of .main in the top-level flex row).
Pages just render <DetailPanel> inline — no manual createPortal,
no context, no prop drilling.

Remove the old #detail-panel-portal div from LayoutShell and the
createPortal wrappers from Dashboard and AgentHealth.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/AgentHealth/AgentHealth.tsx

@@ -1,5 +1,4 @@
 import { useState, useMemo } from 'react';
-import { createPortal } from 'react-dom';
 import { useParams, Link } from 'react-router';
 import {
   StatCard, StatusDot, Badge, MonoText, ProgressBar,
@@ -504,18 +503,15 @@ export default function AgentHealth() {
         </div>
       )}
 
-      {/* Detail panel — portaled to AppShell level for proper slide-in */}
-      {selectedInstance && document.getElementById('detail-panel-portal') &&
-        createPortal(
-          <DetailPanel
-            open={panelOpen}
-            onClose={() => { setPanelOpen(false); setSelectedInstance(null); }}
-            title={selectedInstance.name ?? selectedInstance.id}
-            tabs={detailTabs}
-          />,
-          document.getElementById('detail-panel-portal')!,
-        )
-      }
+      {/* Detail panel — auto-portals to AppShell level via design system */}
+      {selectedInstance && (
+        <DetailPanel
+          open={panelOpen}
+          onClose={() => { setPanelOpen(false); setSelectedInstance(null); }}
+          title={selectedInstance.name ?? selectedInstance.id}
+          tabs={detailTabs}
+        />
+      )}
     </div>
   );
 }