fix(search): surface iTunes stubs and resolve feeds for delisted shows

Shows that left Apple Podcasts (e.g. Daily Wire's in 2021) come back from
the iTunes Search API as metadata-only stub records with feedUrl null.
mapItunesResult dropped them, so The Ben Shapiro Show — the #1 hit for
'ben shapiro' — never appeared in search while sibling shows did.

- Keep feedUrl-less results (feedUrl "" + directoryUrl pointing at the
  Apple page) so delisted shows stay findable.
- Resolve the real feed from the Apple page at subscribe time
  (itunes-feed-resolver: anchor on the collection's adamId, forward-scan
  for the embedded feedUrl; Apple serves page variants where the
  showOffer block sits thousands of chars after the adamId).
- addFeed refuses feedless stubs whose feed can't be resolved instead of
  adding a broken feed; SearchPage surfaces the failure via toast.
- Tests: stub mapping, extractor variants, and an end-to-end subscribe
  over a local HTTP server.

tests/source-searcher.test.ts

@@ -9,7 +9,7 @@
  * search. This test pins the empty-result contract.
  */
 import { test, expect } from "bun:test";
-import { searchSourceByType } from "../src/utils/source-searcher";
+import { searchSourceByType, mapItunesResult } from "../src/utils/source-searcher";
 import { SourceType } from "../src/types/source";
 import type { PodcastSource } from "../src/types/source";
 
@@ -29,6 +29,16 @@ const customSource: PodcastSource = {
   enabled: true,
 };
 
+const itunesSource: PodcastSource = {
+  id: "itunes",
+  name: "Apple Podcasts",
+  type: SourceType.API,
+  baseUrl: "https://itunes.apple.com/search",
+  enabled: true,
+  country: "US",
+  language: "en_us",
+};
+
 test("RSS sources return no directory search results", async () => {
   const results = await searchSourceByType("blocked and reported", rssSource);
   expect(results).toEqual([]);
@@ -38,3 +48,54 @@ test("custom sources return no directory search results", async () => {
   const results = await searchSourceByType("anything", customSource);
   expect(results).toEqual([]);
 });
+
+// ── iTunes stub records (delisted shows) ────────────────────────────────────
+// Shows that left Apple Podcasts (e.g. The Daily Wire's in 2021) remain in
+// the directory as metadata-only records with feedUrl null. They must stay
+// findable — earlier they were dropped entirely, so "ben shapiro" surfaced
+// nothing while the show is the #1 iTunes hit.
+
+test("iTunes results without a feedUrl (delisted shows) are kept, not dropped", () => {
+  const stub = mapItunesResult(
+    {
+      collectionId: 1047335260,
+      collectionName: "The Ben Shapiro Show",
+      artistName: "The Daily Wire",
+      feedUrl: null,
+      collectionViewUrl:
+        "https://podcasts.apple.com/us/podcast/the-ben-shapiro-show/id1047335260",
+    },
+    itunesSource,
+  );
+  expect(stub).not.toBeNull();
+  expect(stub!.title).toBe("The Ben Shapiro Show");
+  // Empty feed marks "unavailable from this directory"; the Apple page URL
+  // is carried for feed resolution at subscribe time.
+  expect(stub!.feedUrl).toBe("");
+  expect(stub!.directoryUrl).toBe(
+    "https://podcasts.apple.com/us/podcast/the-ben-shapiro-show/id1047335260",
+  );
+});
+
+test("iTunes results with a feedUrl keep it and carry no directory fallback", () => {
+  const normal = mapItunesResult(
+    {
+      collectionId: 1487234816,
+      collectionName: "Morning Wire",
+      artistName: "The Daily Wire",
+      feedUrl: "https://feeds.megaphone.fm/BVDWV8747925072",
+    },
+    itunesSource,
+  );
+  expect(normal).not.toBeNull();
+  expect(normal!.feedUrl).toBe("https://feeds.megaphone.fm/BVDWV8747925072");
+  expect(normal!.directoryUrl).toBeUndefined();
+});
+
+test("iTunes results without a collection name stay dropped", () => {
+  const dropped = mapItunesResult(
+    { collectionId: 1, feedUrl: "https://example.com/feed.xml" },
+    itunesSource,
+  );
+  expect(dropped).toBeNull();
+});