Show metadata sections in node panel and preserve them during merge

- Render metadata.sections as labeled blocks in NodePanel sidebar
- Fix memory_merge to carry forward metadata from merged nodes

portal/src/components/NodePanel.tsx

@@ -90,6 +90,18 @@ export default function NodePanel({
         <Field label="Content" field="content" value={node.content} />
         <Field label="Tags" field="tags" value={node.tags.join(', ')} />
 
+        {node.metadata?.sections?.length > 0 && (
+          <div className="mb-3">
+            <label className="text-[10px] uppercase tracking-wide text-gray-500">Sections</label>
+            {node.metadata.sections.map((s: { label: string; body: string }, i: number) => (
+              <div key={i} className="mt-2 bg-gray-800/50 rounded p-2">
+                <div className="text-xs font-medium text-indigo-400">{s.label}</div>
+                <div className="text-sm text-gray-300 mt-0.5 whitespace-pre-wrap">{s.body}</div>
+              </div>
+            ))}
+          </div>
+        )}
+
         <div className="mt-4">
           <label className="text-[10px] uppercase tracking-wide text-gray-500">Connections</label>
           {node.connections.outgoing.length === 0 && node.connections.incoming.length === 0 && (