Keep empty list responses as structured JSON

itemsJsonResponse swapped to a plain-text body when a full inventory was
empty, so profiles/proxies/extensions list returned text on empty but
JSON otherwise — an inconsistent shape for agents. Emit emptyText as a
`note` inside the normal { items, has_more, next_offset } payload instead.
Preserves the empty-inventory guidance (now structured) while paginated
empty pages stay note-free, keeping the full-vs-paginated distinction.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: IlyaasK

src/lib/mcp/responses.ts

@@ -29,15 +29,17 @@ export function itemsJsonResponse<T, U = T>(
   items: T[],
   options: ItemsJsonResponseOptions<T, U> = {},
 ) {
-  if (items.length === 0 && options.emptyText) {
-    return textResponse(options.emptyText);
-  }
+  // Keep the response shape uniform JSON for every list outcome. When empty,
+  // surface emptyText as a `note` (e.g. setup guidance) rather than swapping to
+  // a plain-text body, so agents always get { items, has_more, next_offset }.
+  const note =
+    items.length === 0 ? (options.emptyText ?? options.note) : options.note;
 
   return jsonResponse({
     items: options.mapItem ? items.map(options.mapItem) : items,
     has_more: options.has_more,
     next_offset: options.next_offset,
-    ...(options.note && { note: options.note }),
+    ...(note && { note }),
   });
 }