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.
