Directory: Podcasts and Blogs as a filter, beside the category chips

What a feed is and what it is about are two questions, so they are two
controls that combine: the same .tabs the item filters use for All,
Podcasts and Blogs, and a row of category chips that is always there,
offering only the categories among the feeds the filter lets through. A
picked chip lifts on a second press, so there is no second All.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -12,9 +12,9 @@ The long form, with what was wrong before and how it was found, is in
 
 ### Added
 
-- Directory has a row of chips above it: Podcasts, Blogs, and once Podcasts is picked, each
-  podcast's own iTunes category, the narrower one where a show gives two (Games, not Leisure).
-  Picking one filters the Directory in place.
+- Directory can be filtered to Podcasts or Blogs, and by each show's own iTunes category as a row
+  of chips, the narrower one where a show gives two (Games, not Leisure). The two combine, and
+  both filter in place.
 
 ### Changed