Seeding the roving index from an effect only scheduled the update, so the
focus effect still read the previous index and focused the wrong item for
one render — a screen reader announced both. Seed it where the menu opens
instead. The modes are one exclusive choice, so they also need a group to
scope their checked-ness to.
Arrows/Home/End move a roving focus and Escape hands focus back to the
trigger — the menu unmounts under the focused item, which stranded focus
on <body>. Outside-click deliberately does not refocus: that would steal
focus from whatever was just clicked.
The view mode moves out of Settings into a switcher next to sort, on the
feed and channel pages alike. It leaves the Settings prefs draft for its
own eager save: a toolbar click must not mark that page dirty and trip
its leave-page guard.
lib/feedView.ts owns the vocabulary and maps the old grid/list prefs
forward on read, so nobody's saved choice is lost.
peter