An OPML's page lists its shows' items together, not the shows (#283)

GET /api/feeds/{id}/entries for an OPML or a Patreon creator now lists the
items of the shows in it the person subscribes to, as All Subscriptions does
every feed's. The shows are looked up first and queried by list: an OR with a
subquery, or an IN over one, made a single feed's page a sequential scan of
entries (clarkesworld 10 ms to 26 ms or a second, EXPLAIN on production), so a
single feed keeps its `feed_id = $1`.

The page draws the OPML with its own header and the item list, tabs, search
and sort of any feed, with the feed column showing which show each is from.
A show's scan or change refreshes its OPML's list.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

site/api.mjs

@@ -168,7 +168,7 @@ export const ipx = {
       items: [
         {
           method: 'GET', path: '/api/feeds/{id}/entries', slug: 'get-feed-entries',
-          summary: 'A page of one feed’s episodes, newest first unless sorted.',
+          summary: 'A page of one feed’s episodes, newest first unless sorted. For an OPML list or a Patreon creator, those of the shows in it you subscribe to, together.',
           pathParams: [['id', 'String', 'The feed’s id.']],
           query: 'Page', returns: 'EntryPage', errors: [NOT_SUBSCRIBED],
           example: ipxCurl('GET', '/api/feeds/99-invisible/entries?filter=unread&limit=10'),