Currently Listening and the Directory open at once, or with a spinner (#248)

Both fetched on every visit and drew only when the answer came: Currently Listening took 1.3 s.
fetchPage keeps their answers by address, as the item lists are kept, sharing a request already
on its way; both draw from what is kept at once and again only if the refresh changed them, and
show the spinner with nothing kept. They are fetched ahead with the lists when the page loads,
and when the pointer or a finger reaches their row. Removing an episode from Currently Listening
forgets its kept copy, which would otherwise show it again until the refresh. The preload loop
takes a failed fetch as done instead of leaving an unhandled rejection.

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

web/CHANGELOG.md

@@ -13,7 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- A list opens at once when you have seen it before or the page fetched it ahead: All Subscriptions and the feeds with something unread are fetched when the page loads, and a feed or filter as the pointer or a finger reaches it, then refreshed behind once shown. A list that has to be waited for shows a spinner instead of nothing (#247).
+- A list opens at once when you have seen it before or the page fetched it ahead: All Subscriptions and the feeds with something unread are fetched when the page loads, and a feed or filter as the pointer or a finger reaches it, then refreshed behind once shown. A list that has to be waited for shows a spinner instead of nothing (#247). Currently Listening and the Directory's front page are fetched ahead the same way and open at once (#248).
 
 ### Changed