test(gui): route model-discovery stubs through the pinned transport

The same #697 transport change that broke the root catalog tests also
breaks four cases in gui/tests/models-empty-provider.test.tsx: they stub
`globalThis.fetch`, discovery no longer reads it, and the calls hang on
real DNS until the 5s test timeout.

Reuse the `withStubbedProviderFetch` helper so these configs carry the
caller-owned executor too. Test wiring only.

This one hid from the root suite: `bun run test` covers `tests/`, while
CI runs `cd gui && bun test tests` as a separate step, so the failure
only appeared on the runner.

Author: lidge-jun

gui/tests/models-empty-provider.test.tsx

@@ -8,7 +8,8 @@ import { LanguageProvider } from "../src/i18n/provider";
 import Models from "../src/pages/Models";
 import { EmptyProviderHint } from "../src/pages/models-provider-hints";
 import type { ProviderDiscoverySummary } from "../src/models-groups";
-import { gatherRoutedModels } from "../../src/codex/catalog";
+import { gatherRoutedModels as gatherRoutedModelsDirect } from "../../src/codex/catalog";
+import { withStubbedProviderFetch } from "../../tests/helpers/catalog-provider-fetch";
 import {
   clearModelCache,
   getProviderDiscoveryStatus,
@@ -20,6 +21,14 @@ import { handleManagementAPI } from "../../src/server/management-api";
 let previousLanguage: unknown;
 const originalFetch = globalThis.fetch;
 
+/**
+ * Discovery runs on the pinned outbound transport, which does not read
+ * `globalThis.fetch`. These tests stub that global, so every config gets the
+ * caller-owned executor that hands control back to the stub.
+ */
+const gatherRoutedModels: typeof gatherRoutedModelsDirect = (config, options) =>
+  gatherRoutedModelsDirect(withStubbedProviderFetch(config), options);
+
 beforeEach(() => {
   previousLanguage = (globalThis.navigator as { language?: unknown } | undefined)?.language;
   Object.defineProperty(globalThis.navigator, "language", {