fix: align Channels queryFn return shape with Dashboard

Both Dashboard.tsx and Channels.tsx used the same React Query key
qk.channels.list({}) but returned different data shapes: Dashboard
returned the raw {items, total} object while Channels returned just
the items array. When Dashboard loaded first, React Query cached the
raw object, and Channels' for...of on the cached object threw
'g is not iterable'.

Fix: Channels queryFn now returns the raw API response (matching
Dashboard), and channels extraction uses data?.items ?? []. Added
regression test that pre-seeds the cache with the Dashboard shape.

src/meshcore_hub/web/static/js/spa-react/pages/Channels.test.tsx

@@ -2,7 +2,7 @@ import { screen, waitFor } from "@testing-library/react";
 import { describe, expect, it, vi } from "vitest";
 
 import { Channels } from "@/pages/Channels";
-import { renderWithProviders } from "@/test/renderWithProviders";
+import { renderWithProviders, createTestQueryClient } from "@/test/renderWithProviders";
 import { makeConfig } from "@/test/makeConfig";
 import * as api from "@/utils/api";
 
@@ -69,4 +69,15 @@ describe("Channels", () => {
       expect(screen.queryByText("Public")).not.toBeInTheDocument();
     });
   });
+
+  it("renders correctly when cache was pre-populated by Dashboard (raw object shape)", async () => {
+    mockChannelsApi();
+    const client = createTestQueryClient();
+    client.setQueryData(["channels", "list", {}], CHANNELS);
+    renderWithProviders(<Channels />, { client });
+    await waitFor(() => {
+      expect(screen.getByText("Public")).toBeInTheDocument();
+      expect(screen.getByText("Ops")).toBeInTheDocument();
+    });
+  });
 });

src/meshcore_hub/web/static/js/spa-react/pages/Channels.tsx

@@ -293,16 +293,10 @@ export function Channels() {
     error: queryError,
   } = useQuery({
     queryKey: qk.channels.list({}),
-    queryFn: async ({ signal }) => {
-      const resp = await apiGet<ChannelListResponse>(
-        "/api/v1/channels",
-        {},
-        { signal },
-      );
-      return resp.items || [];
-    },
+    queryFn: ({ signal }) =>
+      apiGet<ChannelListResponse>("/api/v1/channels", {}, { signal }),
   });
-  const channels = data ?? [];
+  const channels = data?.items ?? [];
   const error = queryError ? queryError.message : null;
   const [modal, setModal] = useState<ModalState | null>(null);