Give a feed with no category of its own one of Apple's (#117)

Most blogs and news sites name no <itunes:category>, so they sat under no chip in the
Directory unless an admin set one by hand. When TYPESAFE_KEY is set, a feed's first read, or
a forced refresh, asks TypeSafe's Jev to pick one of Apple's categories or subcategories from
the feed's title and up to 15 item titles, for a catalogue feed with neither its own category
nor an admin's. The answer is stored as the catalogue's category, so a feed is not asked
twice, and an admin can change it. Only on a first read or a forced refresh to keep the calls
down: feeds already subscribed are categorised by one `ipx fetch --force`.

Tried on eight subscribed feeds on 2026-10-04: XDA, Daring Fireball, Ars Technica and The
Verge as Tech News, The Old New Thing as Technology, John D. Cook as Mathematics,
BoardGameGeek as Games, Pluralistic as News Commentary (0.55). About 2,000 input tokens a
feed at $0.042 a million. The likeliest answer is kept however unsure.

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

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- A feed that names no category of its own, as most blogs do not, is given one of Apple's podcast categories from its title and latest items when `TYPESAFE_KEY` is set, so it shows under a Directory chip. Asked when the feed is added, or on a forced refresh for feeds already there; an admin can change it in the feed's settings.
 - Artwork is kept on disk once shown and loads from iPX, not from each publisher's server: fast after the first time, and still there when the publisher's server is not. The admin page sets how much is kept (500 MB by default).
 - `ipx add --list --category News <url>` puts a feed in the Directory for anyone to subscribe to,
   and it stays there when its last subscriber leaves. Run for a feed already in the catalogue,